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Testifying as an expert at the oral trial

  • Procedure

At the oral trial the expert explains the report in person: first the party that called them asks questions, then the other side tries to rebut it.

Updated

What it is

In Colombia's adversarial criminal system, evidence is taken at the public oral trial. The parties ask the judge to summon the experts to be examined and cross-examined on their reports (Law 906 of 2004, art. 412). The expert testifies under oath and the rules for witnesses apply: direct examination, cross-examination, redirect and recross (art. 391). The expert may consult documents, notes and publications to support the answers (art. 417). If physically unable to attend, the evidence is taken by audio and video, or where the expert is (art. 419).

What to document

  • Law 906, art. 412: the parties ask the judge to summon the experts to be examined and cross-examined.
  • Art. 417: the expert is questioned on theoretical training, practical experience, instruments, principles and methods used and their degree of acceptance.
  • Art. 418: cross-examination aims to rebut what was reported and may rely on qualified technical and scientific publications.
  • Art. 420: the judge weighs fitness, the clarity and accuracy of the answers, demeanour when answering and overall consistency.
  • Art. 383: everyone must testify under oath when asked, except for constitutional and legal exceptions; lying under oath is perjury (falso testimonio, Penal Code art. 442).

How it is done

  1. On receiving the summons, confirm date, time, courtroom or video link and the case; report any conflict at once.
  2. Reread the report, the notes and the medical record, and review the literature behind the conclusion.
  3. If the calling party asks for a meeting beforehand, limit it to preparing the presentation, without changing the conclusions.
  4. Take the oath and present your training and experience: they are the basis of the fitness the judge will weigh.
  5. In direct examination, explain findings, method and conclusions in plain language.
  6. In cross-examination, hear the whole question, answer only what is asked and admit the limits of the examination.
  7. Ask permission to consult the report or notes before quoting a figure or detail.
  8. Stay equally neutral with the prosecution and the defence: the expert serves the court, not a party.

Next step: what to do and document

  • Enter the summons in your schedule and ask your institution for leave to attend.
  • Bring a copy of the report and notes, and ask the judge for permission to consult them while testifying.
  • If you do not know or do not remember, say so; if a fact has changed since the report, explain the change and its basis.
  • If illness prevents attendance, notify the court with supporting evidence before the hearing.
  • Official text checked on 2026-11-05 at funcionpublica.gov.co (Law 906 of 2004 and Penal Code, Law 599 of 2000).

Common mistakes

  • Answering with absolute certainty («always», «never») where science gives only probabilities.
  • Arguing with the lawyer or becoming defensive in cross-examination.
  • Using medical jargon without explaining it to the judge.
  • Giving opinions outside one's field, or on the accused's inimputability, which art. 421 forbids.
  • Arriving without rereading the report: contradictions damage credibility.

Test yourself

Think of the answer, then tap the question to see it.

What is the purpose of cross-examining the expert?

To rebut, in whole or in part, what the expert reported; qualified technical and scientific publications may be used for this (Law 906, art. 418).

May the expert consult their notes while testifying?

Yes. Art. 417 gives the expert the right to consult documents, written notes and publications to support and clarify the answer.

What happens if the expert is physically unable to attend the hearing?

They testify by audio and video or another remote system; if none is available, the evidence is taken where they are, before the judge and the parties (art. 419).

In what order is a witness questioned at the oral trial?

First direct examination by the calling party, then cross-examination, then redirect and, if needed, recross (art. 391).

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Connections

← All of forensic medicine

Educational content on forensic and legal medicine; not legal advice and no substitute for the technical guides of Colombia's National Institute of Legal Medicine and Forensic Sciences. Laws change: each page links the official text and says when it was last checked. For a real case, follow the guide in force and ask the competent authority.

Sources: Ley 906 de 2004, Código de Procedimiento Penal (Función Pública, Gestor Normativo, 2004); Ley 599 de 2000, Código Penal (Función Pública, Gestor Normativo, 2000); Forensic evaluations in psychiatry (Chadda RK, Indian Journal of Psychiatry 2013;55(4):393-399) (PubMed Central, 2013).

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