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Law 101: Legal Guide for the Forensic Expert

Requirements for Evidence Admissibility

Photo background of a courtroom. Caption reads, 'Relevancy Requirements for Evidence Admissibility'
National Institute of Justice (NIJ) (see reuse policy).

In order to be admissible, evidence must:

  • Be authentic.
  • Be in good condition.
  • Be able to withstand scrutiny of its collection and preservation procedures.
  • Be presented into the courtroom in specific ways.

All of those requirements are intended to ensure that the fact finder makes his decisions on the basis of reliable information.

Admissible evidence is what it purports to be: It is genuine and not fabricated, contrived, forged or materially altered.

Admissible evidence is offered by an attorney as founded on an indicator of authenticity: A witness or a rule is used to confirm that the evidence is what it is asserted to be.

Evidence is admitted for trial, once the circumstances of collection and preservation are identified:

  • Who seized it?
  • When was it seized?
  • Where has it been since then?
  • How was it preserved?
  • What records exist that confirm the preservation?

Evidence is admitted on the appropriate basis: either testimony from a witness or application of a rule or an agreement.

Most, if not all, of the conditions and circumstances required for evidence admission are established by foundational or predicate questions and/or records.

Before the ultimate question may be asked or the physical object may be shown to the jury or judge, several foundational facts must be established by the attorney seeking its admission. Often, these establishing facts provide answers to the most basic questions:

  • Who?
  • What?
  • When?
  • Where?
  • Why?
  • How?

Foundational questions must be answered before items created by an expert witness can be admitted as evidence, including the expert's own data, report or opinion.

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