At common law the operative rule was formulated in the case of Frye v United
States.
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There, Associate Justice Van Orsdell posed the question: When
does it occur that “a scientific principle or discovery crosses the line between
the experimental and demonstrable stages” (the demonstrable stage being the
stage when it can authoritatively demonstrate something to be true)? Potentially
the point is “difficult to define”. However, “[s]omewhere in this twilight zone
the evidential force of the principle must be recognized, and while courts will
go a long way in admitting expert testimony deduced from well-recognized
scientific principle of discovery, the thing from which the deduction is made
must be sufficiently established to have gained general acceptance in the
particular field in which it belongs”.
Shortly stated, the test is “general acceptance” in the relevant field. However,
mounting problems with expert evidence have caused a rethink of this
approach. And in any event, the Frye test was replaced for federal cases by
statutory provisions in the Federal Rules of Evidence.
Rule 702 is one of the principal provisions in the Federal Rules of Evidence.
Rule 702 applies where “scientific, technical, or other specialized knowledge
will assist the trier of fact to understand the evidence or to determine a fact in
issue”. In this case, evidence may be given by “a witness qualified as an expert
by knowledge, skill, experience, training, or education”. This evidence may be
given “in the form of an opinion or otherwise”.
Scientific evidence can be given only when four requirements are satisfied.
Three of these are stipulated in Rule 702. The fourth requirements namely
absence of bias derives from common law.
Requirement 1: Sufficient Basis
Requirement (1), from Rule 702, says that “the testimony [must be] based
upon sufficient facts or data”. The justification for this is self evident.
Requirement 2: Reliable Principles and Methods
Requirement (2), from Rule 702, stipulates that “the testimony [must be] the
product of reliable principles and methods”. Requirement (2) is significant
because it does not totally defer to outside experts. Instead it permits the
tribunal to scrutinise the principles and methods used to determine that they
are “reliable”. Under the Daubert test, there must be an independent judicial
assessment of the reliability of the evidence.
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Frye v United States 54 App DC 46; 293 F 1013 (DC Cir) (1923)
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Daubert v Merrell Dow Pharmaceuticals 509 US 579, 113 SCt 2786, (1992)
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