Objection to an Expert Report in a Criminal Case: Technical Errors, Contradictions and Effective Defence

An effective objection to an expert report in a criminal case is not merely a statement that the defence does not accept its conclusion. The defence must explain together which data is wrong or incomplete, why the method used was insufficient, how this problem affects proof of the charge, and what step it asks to be taken. An objection tied to a specific page of the report, a supporting record and a concrete question creates a dispute that the court can examine.

Article 67 of the Code of Criminal Procedure (CMK) provides for the interested parties to be given a period, after the report is completed, to notify their objections and to request a new expert examination. The article sets no fixed two-week period for objection. Hearing the expert in court, putting questions to them, and obtaining a scientific opinion from one's own specialist are also tools available to the defence. Which tool to choose depends on the nature of the problem in the report and the stage of the file. [1]

What does an expert report determine in a criminal case?

A court-appointed expert is consulted to clarify a question that requires specialist, special or technical knowledge. Matters that can be resolved through general knowledge and experience, or through the judge's legal knowledge, cannot be left to an expert. The appointment may be made by the public prosecutor during the investigation, or by the judge or court during the trial. The parties may request that an examination be carried out; the power to appoint an expert for a judicial task does not belong to them. [1, CMK Art. 63]

A report contributes to the proceedings by making the document, measurement or technical finding used understandable. For this, the basis of the conclusion reached must be traceable. Where a report states that a device was examined but does not explain which records were analysed by which method, it does not constitute a sufficient technical justification. Article 55 of the Expert Witness Regulation counts the examination method, the scientific and technical bases and a reasoned conclusion among the elements of a report. [2]

The report does not pass judgment in place of the court. The court assesses whether the technical findings are consistent with the other evidence in the file, whether they are lawful, and whether they prove the elements of the offence. Under CMK Art. 217, a judgment must rest on evidence brought before the court and discussed there; an offence may be proved only with evidence lawfully obtained. The fact that a report bears an institutional letterhead or is signed by several persons does not replace this assessment. [1, 2]

For this reason, the aim of the defence should not be to reject every report in its entirety. Sometimes the measurement part of the report is correct but the conclusion drawn from that measurement is problematic. Sometimes the conclusion favours the accused but the reasoning is insufficient. A sound defence clearly separates the findings it accepts and concentrates the debate on the points that affect the outcome of the case.

Time limit for objecting to an expert report and the first steps to take

What do "two weeks" and "three days" mean in the CMK?

In civil cases, Article 281 of the Code of Civil Procedure (HMK) provides a two-week period running from notification of the report. That provision cannot be transferred directly to a criminal file. In criminal procedure, CMK Art. 67(5) orders that a period be given to the interested parties for an objection or a request for a new examination; it does not fix a number of days. The content of the decision in the concrete file, the accessibility of the report and its annexes, the form of notification and the start of the period set must be examined together. [1, 3]

The three days in the same paragraph are not the party's period for objecting to the report. They relate to the reasoned decision to be given where the requests are rejected. Writing "within the statutory three-day period" or "within the two-week final period" in an objection petition, using a template taken from the internet, may misstate the real procedural position in the file.

The absence of a fixed statutory number of days does not mean that an objection may be deferred. When the report is learned of, the period granted and the hearing date must be recorded; if technical assistance is needed, work should begin immediately. If the report has been newly delivered, its annexes are missing or there is a problem with access to the examination, these must be stated concretely and a suitable period must be requested to allow the defence to be prepared. CMK Art. 67(6) does not consider a request for a scientific opinion alone sufficient reason to ask for an additional period separately. These two situations must not be confused. [1]

Which documents should be read together as soon as the report arrives?

The first reading should begin with the appointment decision, before the conclusion section. Without knowing what the expert was asked, it cannot be assessed whether the answer given is adequate. The whole report, its annexes, earlier reports and the records on which the examination is based should then be brought together. If an annex is missing, the document must record which annex is absent and which result cannot be verified as a consequence.

The working file should specifically contain: the appointment decision; the date and signature details of the report; the record showing that a copy of the report was given or notified; the decision on the period granted; the delivery records of the documents and objects subject to examination; earlier objections; and any scientific opinion. The list and count of items delivered to the expert under seal, and the documentation by minutes of the opening and resealing of the seals, are separately regulated in CMK Art. 66(7). [1]

The backbone of an effective objection: finding, basis, effect and request

The statement "the report is not amenable to review" remains abstract unless it explains which review could not be carried out and why. A more useful formulation is this: "The starting amount used in the report's calculation table differs from the amount in the bank statement; the source of this difference has not been explained. As the result of the calculation depends on this starting amount, we request that the calculation be redone, with reference to the relevant record." Here the problem, the basis, the effect on the result and the requested step all appear together.

The table below is a working arrangement that may be used in preparing objections specific to the file. The examples are hypothetical; each row does not apply to every report.

This arrangement may also be used as a short summary on the first page of a multi-page petition. However, the table does not replace explanation. Under each important objection, the relevant document and report section should be shown, and it should be explained which aspect of the charge may change once the problem is resolved. In this way the court can see the link between the request and the dispute.

How are data, method and calculation errors investigated?

Is the data used in the report really the data in the file?

The date, version, person or transaction to which the document relates, and the scope of the portion taken into the report, must be checked. In an accounts report, two lines bearing the same description may be two separate transactions; equally, a single transaction may appear in different statements. Rather than inferring duplication from a similar appearance, the defence should match the transaction number, date, amount and source of the record.

In digital examination too, the first question is which device or copy was examined. The NIST guide on computer forensics treats verification of the integrity of a copy by hash values as part of technical examination. That check provides information about data integrity at particular stages; it does not on its own prove who created the file or whether the content reflects material truth. Technical integrity and attribution to a person are separate questions. [8] For the procedural and documentary aspects, the article Digital evidence in criminal proceedings may also be consulted.

The fact that the report does not include a record does not show that the record was necessarily altered. The correct request is to secure the record and the explanation that makes the examination possible. Where a claim of data corruption is raised, its concrete basis, the finding it affects and the proposed verification step should be stated. Possibility and actual occurrence should not be presented in the same terms.

Is the method appropriate for the data and the question?

The way in which the method is applied to the data in this file matters as much as its name. The defence should distinguish the following questions: Which operation was carried out? From where were the inputs taken? Which assumptions were accepted in order to reach the result? Is there a check that could not be carried out because of missing data? Is the result stated with certainty within the scope that the explained examination actually permits?

The technical expert's task is to answer these questions with the knowledge of their own field. The lawyer's task is to make visible the step that is not explained and its legal significance. A lawyer should not declare, on personal conviction, that a calculation requiring expertise is definitely correct; they should frame the question that makes a re-examination possible. The method and reasoned-conclusion structure of the Expert Witness Regulation provides the legal basis for this approach. [2, Art. 55]

In a report, the expressions "could not be determined", "found consistent" and "determined with certainty" do not carry the same meaning. The defence should examine whether a cautious finding in the report has been turned into definite knowledge in the indictment or in the opinion of the prosecutor. A conclusion that the technical report does not state cannot be made to appear in it merely by referring to the report.

The effect of a calculation error on the result must be shown

A wrong addition, a unit conversion error, a wrong date range or the use of the same data twice may be easily noticed problems. Even so, not every error changes the outcome of the case. For example, a small arithmetic difference in a total may not affect the basic premise regarding the existence of the offence, but it may matter for the amount of damage or for another legal assessment.

The objection should therefore be built in two layers: first the reason why the calculation is wrong, then which area of assessment would change with the correct calculation. Where a legal consequence is to be drawn from a change in the amount, its basis in the relevant offence type must be separately shown. No step should be left out between the technical error and the legal consequence.

The limits of the expert's task: technical explanation and assessment of guilt

CMK Art. 67(3) prohibits an expert from going beyond their field of expertise and from making the legal classifications and assessments that the judge must make. The same limit appears in Article 3 of Law No. 6754 on Expert Witnesses. An expert may explain technical data; they cannot determine of which offence the accused should be convicted. [1, 4]

For example, an engineer may examine the safety arrangement of a machine, its operating conditions or the technical effect of a particular precaution. How these findings are linked to the criminal liability of a specific accused, together with the duty, conduct, causation and elements of the relevant offence, is for the court's assessment. A percentage of fault stated in a report cannot be accepted as the whole of this legal reasoning.

The defence should identify the exact sentence that goes beyond the limit of the task and explain why it is separate from the technical finding. The presence of a legal assessment in a report does not mean that every measurement within it is automatically disregarded. The debate should be built around which part has the value of a technical examination and which part falls within the court's judicial authority.

Where the appointment decision itself consists only of a broad question such as "is the accused at fault?", the defence may request that the technical questions be made concrete. When it is examined which conduct, under which conditions and with which effect on which result, both the expert's field of task and the court's responsibility for the decision become clear.

Contradictory reports: a supplementary report or a new expert?

The difference between the first report and a supplementary report should be examined by first asking what has changed. A new document may have entered the file, the earlier data may have been corrected, or the method may have been reassessed. A change that is explained and can be verified is not the same as reaching the opposite conclusion without giving any reason. The defence should compare the earlier and new reports not only through their conclusion sentences but through their bases.

Article 3(7) of Law No. 6754 accepts, as a principle, that a report is obtained once on the same subject; it allows a supplementary report to be obtained where there is an omission or an ambiguity. CMK Art. 67(5) expressly regulates a request for a new expert examination. When these provisions are read together, the approach that a report should be obtained until the desired result is reached cannot be accepted; the reason why a new examination is necessary must be explained. [1, 4]

The table is not a ladder that must be climbed in the same order in every file. Sometimes it is necessary to request a new examination directly; sometimes a detailed supplementary report is sufficient. The element that strengthens a request for a "new panel" is an explanation of why the existing expert cannot remedy the same deficiency. If a panel is requested, the necessary fields of expertise should be stated before the number of persons.

Court of Cassation: not every different result requires a new report

The decision of the Criminal General Assembly of the Court of Cassation of 5 April 2016, E.2015/1149, K.2016/182, illustrates this distinction. In a work accident in which two persons died, the reports differed as to whether the accused was found primarily or secondarily at fault. The majority of the Assembly accepted that there was no technical contradiction as to the manner in which the event occurred and the negligent conduct, and that the difference in the legal assessment of fault did not make a new examination mandatory; it therefore rejected the objection of the Chief Public Prosecutor's Office. Nine members voted in favour of accepting the objection. [5]

This decision does not mean that all contradictions in reports are trivial. The conclusion the defence may draw is this: it must be shown whether the contradiction lies in the technical fact, in the assumption or in the legal consequence. Where the technical problem has been sufficiently clarified, simply placing different conclusion sentences side by side may not be enough to justify a new examination. The earlier-law transcriptions of the decision should not be used in place of the current text of the law.

What does an expert opinion add to the defence?

CMK Art. 67(6) allows a scientific opinion to be obtained from a specialist on the event under trial or on an expert report. This differs from the court's appointment of an expert. The opinion of the specialist chosen by the defence is assessed through its reasoning, the data it uses and its method of examination. The fact that the party pays for the opinion does not render it worthless of itself; nor does an academic title ensure that the opinion is correct of itself. [1]

The task given to the specialist should not be an instruction that predetermines the result, such as "refute the report". The problem to be examined, the documents accessible and the technical questions to be answered must be stated clearly. The specialist should also show the limits of their assessment, including findings favourable or unfavourable to the defence. If the defence has not had access to a decisive record of the file, that deficiency should not be concealed.

The section of the Lawyers' Handbook II on expert reports suggests that the defence should attend to the subject from the investigation stage onwards, and consider together the scientific opinion, supplementary report, new examination and the possibility of putting questions. This recommendation shows the importance of not leaving technical preparation until the day of the hearing. [6, pp. 100–101]

When an opinion is obtained, it should not be enough simply to attach it to the petition. It should be explained which finding conflicts with the court's report, why this is important and what examination it requires. Where necessary, a request may be made under CMK Art. 68(3) for the expert who prepared the opinion to be heard at the hearing. It should not be assumed that an additional period will be granted merely on the ground that a scientific opinion will be obtained. [1]

How are questions put to the expert at the hearing?

CMK Art. 68 regulates the court's power to summon the expert to the hearing to explain the report. CMK Art. 201 grants the lawyer participating as defence counsel or representative the right to put questions directly to the expert, in a manner consistent with hearing discipline. The accused and the intervening parties put their questions through the presiding judge or the judge. If an objection is raised to a question, the presiding judge decides whether it is to be asked. [1]

The request for summons should state which point of the written report needs explanation. Hearing of an expert is not an automatic step that takes place upon every request. Showing the relationship between the questions expected to be answered and the outcome of the file makes the necessity of the request understandable.

Sequence of questions with strong persuasive force

A sequence of questions should produce answers that are understandable and capable of being verified. At the first stage, the record examined and the limit of the task are identified. Then the method, assumptions, checks and result are addressed. Having a single issue in each question makes it easier to record the answer given and to link it to the next question.

A short question does not mean that the answer must be reduced to "yes" or "no". Where a technical matter requires explanation, the expert's explanation should be heard. The defence may then narrow the answer to one concrete point: "So in this calculation you are saying that you did not use the relevant record?" A follow-up question of this kind must genuinely rest on the previous answer.

Effective oral defence shows the limit of the inference rather than attacking the expert's credibility. Raising one's voice, or repeating the same question after an answer has been given, does not clarify the technical dispute. Where the expert has accepted a limitation, counsel may convey it to the court without exaggeration: "The explanation shows that the total in the report was produced with an incomplete record; we therefore request that the calculation be redone with all records."

When a question is blocked, the discussion should focus on the exact content of the question, what it is intended to clarify and the reasons for the refusal, rather than on the person. Under CMK Art. 219–222, it matters for later review that important questions and answers, requests and decisions are accurately reflected in the minutes. Counsel's private notes do not replace the hearing minutes. [1]

Access to technical data and the Constitutional Court's defence guarantee

Discussing the result of a report may require more than seeing the result page. Where the examination depends on basic data, it is important that the defence can examine that data or obtain an effective technical verification. An access request should be framed by stating the record requested, the examination to be carried out and its connection with the charge.

In Yankı Bağcıoğlu and Others, Application No. 2014/253, judgment of 9 January 2015, the Constitutional Court (AYM) dealt with the refusal of requests for examination of digital data on which the conviction rested, or for images of that data to be provided. The Court assessed, in terms of equality of arms throughout the proceedings as a whole, that the defence had not been able to raise effectively its objection concerning the accuracy of the data, and found a violation as regards the applicants found admissible. It ordered that the decision be sent to the relevant court for retrial. [7, §§ 55–78, 82 and operative part]

The decision does not order that every expert request be accepted or that every restriction on access be treated as a violation. The Constitutional Court explains that the primary determination of the need for a technical examination lies with the courts of first instance and that restrictions on access must be examined together with the necessary safeguards. The matter the defence must show is how a concrete restriction affected the possibility of testing the decisive evidence. A finding of violation is not, by itself, an acquittal judgment.

How is an objection built in a hypothetical file?

Let us assume that in a criminal file the expert has calculated a total amount from the transaction statements. In the report, two lines bearing the same transaction number have been included in the total; one appears in the main statement and the other in the supplementary list. Further, the report attributes the whole of this amount to the transaction of a particular accused. In this example there are two separate problems: whether the records are in fact two separate transactions, and what data the link between the calculated amount and the accused rests on.

The defence should first examine all the records. If it emerges that the same number was used for different transactions in different systems, the claim of duplication should be abandoned. If it is confirmed that the two entries are two presentations of a single transaction, a request is made to recalculate the total, showing the transaction identifier and the document locations. The question of attribution is addressed under a separate heading; even if the total is correct, it may still be necessary to determine separately who carried out the transaction.

The statement at the hearing may be made in the following order: "There are two points in the report that we dispute. The first is that this transaction appears twice in the total. The second is that the report attributes the amount calculated to the accused without explaining which record it used. We request that the relevant records be obtained, that the possibility of duplication be checked, and that the basis for accepting attribution be explained." This wording turns the technical problem into requests that the court can decide.

An example of a reasoned request that may be used in a petition

The following example relates only to the hypothetical accounting dispute described; the dates, pages, records and requests of the concrete file must be verified before it is adapted.

"In the calculation section of the report under objection, the main statement record and the supplementary list record bearing the same transaction number have been included in the total as separate transactions. The report contains no explanation showing that the records relate to two separate transactions. As this distinction affects the total amount and the scope of the transactions attributed to the accused, we request that the relevant records be obtained from their source and opened to the examination of the parties.

If it is understood that the records relate to a single transaction, we request that the duplicated amount be removed and the calculation redone; if it is maintained that they relate to separate transactions, we request that this distinction be explained with its supporting documents and transaction identifiers. We further require that, for each transaction attributed to the accused in the report, the data by which it has been linked to the accused be shown separately.

On these matters, we request that a supplementary report with specified questions be obtained and that the expert be heard at the hearing for such explanations as may be considered necessary; and, if it is understood that the deficiency cannot be remedied by these means because of the expert's field or the scope of data, that a new examination be carried out by an expert in the appropriate field. We request a reasoned decision on our requests."

The value of this example does not lie in its length. What matters is that the objection rests on verifiable records, is open to contrary explanation, and that the request is directed at resolving the identified problem. Once the technical deficiency is remedied, the result may also turn against the accused; an effective defence should be built on the real position of the file, without disregarding that possibility.

Objection to a report, challenge to the expert and complaint are different routes

An objection to a report concerns the content or manner of the examination. Challenge of an expert, on the other hand, is a separate request regulated in CMK Art. 69, linked to the grounds that require the recusal of a judge. The person requesting the challenge must show the ground and the facts on which it rests. The mere fact that a report unfavourable to the accused has been issued does not prove that the expert is biased. [1]

An application to the regional board of expert witnesses does not replace the technical objection within the proceedings either. Under Article 14(3)–(4) of Law No. 6754, the regional boards cannot review the accuracy of a report from the standpoint of its specialist or technical content; applications concerning such content are rejected without examination. Review of attitude, conduct and compliance with the law, and the criminal court's assessment of the report, are separate procedures. Where institutions providing expert services under a special law are concerned, the scope exception of the Law must also be observed. [4, Arts. 1/3 and 14]

A claim that a report is false is also not the same as a difference of scientific opinion. Article 58 of the Expert Witness Regulation points to criminal liability for an opinion deliberately contrary to the truth. For this, the concrete facts must be separately assessed against the conditions of the relevant offence. The defence should not use a threat of complaint as a means of pressure merely because it has not received the technical answers it wanted. [2]

If an objection is rejected, how is the defence continued?

First the reasons for the refusal should be examined: has the court accepted that the matter has already been explained, that the request has no effect on the decision, or that it is aimed only at prolonging the proceedings? The defence's subsequent statement should respond to the specific point in that reasoning. Rather than submitting the same petition unchanged, it is more effective to show the unexamined record or the new finding.

CMK Art. 207 provides that a request to present evidence may not be refused merely because it was notified late. However, the grounds of unlawfulness under CMK Art. 206, the lack of effect on the decision and the making of a request solely to prolong the proceedings are separately assessed. These provisions do not render the period for objecting to a report insignificant; the reason for the delay and the necessity of the examination must be clearly explained. [1]

An objection to a report is not an appeal remedy. When a refusal decision is given, whether a separate objection route is open depends on the type of decision and the relevant specific provision; it cannot be said that every refusal may automatically be taken to a higher court. For objections to court decisions, the framework of CMK Art. 267 is taken into account. Where the appeal lies against the final judgment, the way in which the refused technical examination affected the judgment must be explained. [1]

In the defence on the merits, the technical objection is again tied to its legal consequence. It must be shown which part of the report has lost its probative force, whether other evidence remedies this deficiency and which element of the offence is not established. If it is not established that the accused committed the offence charged, an assessment of acquittal arises under CMK Art. 223(2)(e); this is not the "dismissal of the case" that results from insufficiency of evidence. Discussion of the evidence in the reasons for the judgment and the showing of rejected evidence are also important under CMK Art. 230. [1]

For details related to this subject, you may read our article on HTS and base station records.

For details of this subject, you may read our article on objection to an expert and forensic medicine report in a malpractice case.

Conclusion

An effective objection to an expert report in a criminal case is a defence exercise that links the technical examination to legal reasoning. The data on which the report rests must be seen, the method understood, the contradiction identified in the right place, and the way in which the deficiency affects proof of the charge explained. A route should then be chosen in accordance with the problem: explanation, supplementary report, new examination or scientific opinion.

The persuasive force at the hearing also derives from this preparation. Questions focused on a single issue, comments that do not exceed the limits of the report and requests accurately reflected in the minutes give substance to the defence. The measure of a strong objection is not how harshly the report is opposed, but whether it can be clearly shown to the court which technical problem must be solved, and why.

Frequently Asked Questions

Within how many days must an objection to an expert report be made in a criminal case?

CMK Art. 67(5) does not fix a number of days; it provides for a period to be given for an objection or a request for a new examination. The period decision in the file and the notification records must be examined. The two-week period in civil cases does not apply directly to a criminal file. [1, 3]

Is the three-day period in the law the accused's period for objection?

No. The three days in CMK Art. 67(5) relate to the reasoned decision to be given where the requests are rejected. The defence's period is determined by the decision given by the authority that ordered the examination. [1]

If no objection is made to an expert report, does the report become final?

A report does not become final like a judgment; it is subject to the court's assessment. Nevertheless, failure to raise the objection in good time and in a concrete form may make it harder for the technical problem to be clarified in the proceedings. The period granted must be complied with. [1, 2]

Must the court appoint a new expert for every objection?

No. A deficiency may be remedied by explanation or by a supplementary report; some differences may not require a new technical examination. A request for a new expert must show why the existing examination is insufficient and which problem cannot be solved. [1, 4, 5]

Can the defence obtain a report from its own expert?

Under CMK Art. 67(6), the defence may obtain a scientific opinion from its own expert. This opinion is not based on the same appointment as the expert report appointed by the court. The method and data of the opinion must be explained, and where necessary a request may be made to hear the expert. [1]

Is an additional period always granted to obtain an expert opinion?

No. CMK Art. 67(6) provides that an additional period cannot be requested separately for this reason alone. If there is another problem affecting the preparation of the defence, such as no access to the annexes of the report, that problem must be raised on its own concrete grounds. [1]

Can a lawyer put questions directly to an expert?

A lawyer participating in the hearing as defence counsel or representative may put questions directly to the expert under CMK Art. 201, in a manner consistent with hearing discipline. The summons of the expert to the hearing may be requested from the court under CMK Art. 68. [1]

Does an expert's legal assessment invalidate the whole report?

An expert's legal classification and assessment are prohibited. However, the technical findings of the report and the statements that exceed the limit of the task should be examined separately. It does not automatically follow in every case that the whole report has no value. [1, 2, 4]

Does a complaint to the regional board replace a technical objection to a report?

No. The regional board cannot review the content of a report from the standpoint of its specialist or technical information. A technical dispute must be raised before the judicial authority examining the file; the scope of an application concerning attitude, conduct and compliance with the law is assessed separately. [4]

Is finding an error in a report sufficient for acquittal?

Not every error on its own requires acquittal. It is assessed which finding the error affects and whether all the evidence in the file proves the elements of the offence. Where it is not established that the accused committed the offence, CMK Art. 223(2)(e) applies. [1]

Sources and legal bases

[1] Law No. 5271, Code of Criminal Procedure; in particular Arts. 63–69, 201, 206–207, 215–217, 219–223, 230 and 267. Ministry of Justice text.

[2] Expert Witness Regulation, Official Gazette No. 30143 of 3 August 2017; in particular Arts. 5, 55–56, 58–60. Text of the Expert Witness Department.

[3] Law No. 6100, Code of Civil Procedure, Art. 281; for the distinction of periods in civil and criminal proceedings. UYAP legislation record.

[4] Law No. 6754 on Expert Witnesses; in particular Arts. 1/3, 3 and 14. Text of the Expert Witness Department.

[5] Criminal General Assembly of the Court of Cassation, 5.4.2016, E.2015/1149, K.2016/182; difference between expert reports and the necessity of a new examination. Record of full text.

[6] Lawyers' Handbook II: Determining Defence Strategy and Drafting Petitions; EU–Council of Europe joint programme, "Strategies to be Followed Regarding Expert Reports", pp. 100–101. PDF on the Ministry of Justice site.

[7] Constitutional Court (AYM), Yankı Bağcıoğlu and Others [Plenary], B. No: 2014/253, 9.1.2015; in particular §§ 55–78, 82 and operative part. Official decision record; full text examined.

[8] NIST, Guide to Integrating Forensic Techniques into Incident Response, SP 800-86, August 2006, §4.2.2; verification of the integrity of data copies. NIST publication. It is not used as a binding procedural rule under Turkish law.