Fishback v. People

851 P.2d 884, 17 Brief Times Rptr. 691, 1993 Colo. LEXIS 396, 1993 WL 128506
CourtSupreme Court of Colorado
DecidedApril 26, 1993
Docket92SC68
StatusPublished
Cited by64 cases

This text of 851 P.2d 884 (Fishback v. People) is published on Counsel Stack Legal Research, covering Supreme Court of Colorado primary law. Counsel Stack provides free access to over 12 million legal documents including statutes, case law, regulations, and constitutions.

Bluebook
Fishback v. People, 851 P.2d 884, 17 Brief Times Rptr. 691, 1993 Colo. LEXIS 396, 1993 WL 128506 (Colo. 1993).

Opinions

Chief Justice ROVIRA

delivered the Opinion of the Court.

We granted certiorari to review the decision of the Colorado Court of Appeals in People v. Fishback, 829 P.2d 489 (Colo.App.1991), affirming the trial court’s admission of identification testimony based on a comparison of deoxyribonucleic acid (DNA) obtained from the defendant’s blood with the DNA from a semen sample recovered from the victim. The admissibility of DNA identification evidence is a question of first impression for this court.

I. FACTUAL AND PROCEDURAL BACKGROUND

The defendant was convicted of first degree sexual assault, second degree burglary, and mandatory sentence violent crime.

The evidence connecting the defendant to these crimes included the victim’s identification of defendant, fingerprint evidence, and expert testimony that a DNA profile from seminal fluid obtained by a medical examination of the victim after the assault matched a DNA profile from a blood sample taken from defendant.

The trial court conducted an evidentiary hearing on defendant’s motion to suppress the DNA typing evidence. At the hearing two witnesses testified: Dr. William Set-zer, the director of the University of Colorado Health Sciences Center DNA Diagnostic Laboratory1 who was qualified as an expert in the area of molecular biology, genetics, and “DNA testing”; and Dr. Lisa Forman, an employee of Cellmark Diagnostics,2 who was qualified as an expert in population genetics. At the conclusion of the hearing, the trial court ruled that DNA typing evidence was admissible under both CRE 702 and the test articulated in Frye v. United States, 293 F. 1013 (D.C.Cir.1923).

The court of appeals affirmed, holding DNA typing evidence to be generally accepted within the relevant scientific communities and thus, admissible under the standard set forth in Frye. We affirm.

II. SCIENTIFIC BACKGROUND

A basic understanding of the scientific principles and techniques underlying DNA typing is essential in order to understand the legal issues relating to its admissibility. DNA typing for forensic purposes utilizes a technique in which the characteristics of a suspect’s genetic structure are profiled and compared to the genetic structure found in material such as blood, hair, or semen recovered from a crime scene. The two profiles are then compared to see if they match. If the two profiles match, the statistical significance of such a match is calculated to determine the likelihood of a match occurring between the profile derived from the crime scene sample and a third person who is not the suspect. The process by which this is accomplished can be divided into three parts: (A) The theory underlying DNA typing; (B) the techniques which apply that theory; and (C) the method of calculating the statistical significance of a declared match.

A. DNA theory.

DNA is the material that determines the genetic characteristics of all living things. The significant feature of DNA for forensic purposes is that, with the exception of identical twins,3 no two individuals have identical DNA. Furthermore, because DNA does not vary within a particular individual, a DNA molecule found in one cell will be identical to the DNA found in every other cell of that person.

In human beings, every cell that has a nucleus contains DNA which is distributed [886]*886across forty-six sections of the nucleus of the cell. These sections are referred to as chromosomes, and they form twenty-three pairs: half of each pair are inherited from the mother, the other half from the father. These twenty-three chromosomes contain thousands of genes which comprise the total genetic makeup of an individual. “Alleles” are polymorphisms of a given gene, i.e., they vary from one individual to the next, and since each gene is represented by two copies (one from each parent) two alleles are inherited for each gene. When alleles that constitute a pair (or “genotype”) differ, the person is said to be “heterozygous” for that allele. When a person inherits the same allele from both parents, that person is said to be “homozygous” for that allele.

A DNA molecule is a double helix, resembling a ladder that has been twisted which, if unraveled, would be approximately six feet in length. The “sides” of the ladder are composed of a chain of deoxyri-bose sugars and phosphates, while the “rungs” are composed of one pair of the following nucleotide bases: Adenine (A), Cytosine (C), Guanine (G), and Thymine (T). According to the “base pair rule,” A can only bond with T and G can only bond with C. Thus, the order of the bases on one side of the rung will determine the order on the other side.

Each DNA molecule contains approximately 3 billion base pairs, or rungs, the vast majority of which (99%) do not differ from one human being to the next. It is this similarity in rungs which accounts for the human characteristics of human beings. Certain sections of the DNA molecule differ {i.e., they are allelic) from individual to individual, race to race, and ethnic group to ethnic group. These areas of variation are called “polymorphic sites.” At some polymorphic sites short sequences of base pairs repeat in tandem, over and over again. The core sequence comprising a given allele is called a Variable Number Tandem Repeat (VNTR) and may contain just a few or as many as several dozen nucleotide bases. Because the number of times the core sequence of base pairs repeats may vary among individuals, the length of a given allele, measured in numbers of base pairs, may also vary. For instance, one person may have a particular allele in which a given core sequence repeats only ten times, whereas that same allele in another person may contain the same VNTR that repeats 100 times.

There are approximately three million alleles on each human DNA ladder. While all of these alleles are polymorphic, some are much more polymorphic than others. Forensic DNA typing utilizes a small number of highly polymorphic or “hypervaria-ble” sites.

A DNA profile arrived at through the isolation and comparison of the lengths of several highly polymorphic alleles is known as restriction fragment length polymorphism (RFLP) analysis.4 A DNA profile constructed by means of RFLP analysis is accomplished through the following techniques.

B. Techniques of RFLP analysis.

1. Extraction of DNA. The biological material that contains DNA must ordinarily be separated from the material in which it is found. Once separated, the DNA is extracted from the samples by a chemical treatment which releases the DNA. An enzyme is then added to digest cellular material other than DNA, rendering a purer DNA sample.5

[887]*8872. Restriction or Digestion. The DNA is then mixed with restriction enzymes which “cut” the DNA molecules into fragments at specific base sequences. These enzymes recognize particular sequences of base pairs and sever the DNA molecule at all sites along the three billion base pair length of the molecule where the targeted base pair sequence occurs. This results in numerous DNA fragments which can vary in length from a few base pairs to several thousand.6

3. Gel Electrophoresis.

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Bluebook (online)
851 P.2d 884, 17 Brief Times Rptr. 691, 1993 Colo. LEXIS 396, 1993 WL 128506, Counsel Stack Legal Research, https://law.counselstack.com/opinion/fishback-v-people-colo-1993.