The Introduction of Scientific Evidence in Criminal Cases
| Publication year | 1993 |
| Pages | 273 |
| Citation | Vol. 22 No. 2 Pg. 273 |
1993, February, Pg. 273. The Introduction of Scientific Evidence in Criminal Cases
Scientific evidence is being used in an increasing number of criminal cases. An expert witness offering testimony about such matters as scientific experiments, test results and psychological syndromes appeals to the jury's desire for "the facts" and creates a scientific aura that may significantly strengthen a case.
Criminal lawyers have long been familiar with certain types of expert scientific testimony. Experts have testified for years about the results of fingerprint comparisons, ballistics tests, alcohol concentration in the blood and handwriting examination. There is a clear trend among criminal lawyers toward using more expert testimony. There is also an equally clear trend among the courts to allow the introduction of more and different types of such testimony.
This article explores issues relating to the admissibility of expert testimony. The two legal tests used to evaluate such testimony are discussed, as are specific applications of these tests and some miscellaneous issues. The use of expert testimony in sanity cases is not discussed.
Since 1923, the Frye test(fn1) has been the traditional and most widely used way of judging the admissibility of scientific evidence. The defendant in Frye v. U.S. attempted to introduce evidence of a systolic blood pressure test which he claimed showed that he was telling the truth when he denied responsibility for the offense. After the trial court rejected this offer, the District of Columbia Court of Appeals affirmed the conviction. Acknowledging that it is not always easy to determine precisely when a scientific test moves from the experimental to the demonstrable state, the appellate court held that scientific evidence should not be admitted unless the principles on which the procedure is based are "sufficiently established to have gained general acceptance in the particular field in which it belongs."(fn2)
The second test for the admissibility of scientific evidence is set forth in Colorado Rules of Evidence ("C.R.E.") 702, which allows the introduction of "scientific, technical or other specialized knowledge [if it] will assist the trier of fact to understand the evidence or to determine a fact in issue." This is obviously an easier foundational hurdle for counsel to clear than the Frye test.
When introducing scientific evidence, counsel first must determine which standard applies. The rule in Colorado, set forth in People v. Hampton,(fn3) is that the Frye test should be applied "to novel scientific devices and processes involving the manipulation of physical evidence."(fn4) The Hampton court suggested that, under this definition, the Frye test would be applicable to polygraph examinations, experimental blood typing, processes, voice and bite mark identification and microscopic examination of gunshot residue. In theory, scientific evidence which does not fit the Hampton description should be evaluated using C.R.E. 702.
The test of C.R.E. 702 was described further in the recent Colorado Supreme Court case of People v. Fasy.(fn5) During the trial of the defendant for sexual assault on a'child, the prosecution introduced evidence from a psychologist that the victim suffered from post-traumatic stress disorder. The Court of Appeals reversed the defendant's conviction,(fn6) finding that the testimony amounted to an improper assertion that the victim was being truthful on a particular occasion.(fn7) The Colorado Supreme Court reversed the Court of Appeals and reinstated the conviction, finding the testimony admissible under C.R.E. 702.
The Supreme Court noted that the C.R.E. 702 standard should be employed on a case-by-case basis. It directed trial courts to ask the following question: "On this subject can a jury from this person receive appreciable help."(fn8) [Italics in original.] The court then found that the psychologist's testimony assisted the jury in understanding the victim's behavior---particularly her symptoms---and her delay in notifying the authorities after the incident.
In Hampton,(fn9) the Colorado Supreme Court used the C.R.E. 702 test to approve the introduction of "rape trauma syndrome" evidence. The court held that, under C.R.E. 702, rape trauma syndrome
In Campbell v. People,(fn10) the Colorado Supreme Court held that C.R.E. 702 was the proper test to determine the admissibility of expert testimony relating to the reliability of eyewitness identification. The court...
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