Caldwell v. State
| Decision Date | 03 July 1990 |
| Docket Number | No. S90A0463,S90A0463 |
| Citation | 393 S.E.2d 436,260 Ga. 278 |
| Parties | CALDWELL v. The STATE. |
| Court | Georgia Supreme Court |
Thomas J. Charron, Dist. Atty., Marietta, Michael J. Bowers, Atty. Gen., Atlanta, Debra Halpern Bernes, Asst. Dist. Atty., Nancy I. Jordan, Asst. Dist. Atty., Jack Mallard, Chief Asst. Dist. Atty., Robert E. Flournoy, Cobb Judicial Circuit, Marietta, C.A. Benjamin Woolf, Atty., State Law Dept., Atlanta, for the State.
This case, in which the prosecutor seeks a death penalty, is here on pre-trial review under OCGA §§ 17-10-35.1 and -35.2.
1. The defendant moved the trial court to prohibit the introduction of DNA identification evidence. Between May 8, 1989, and October 31, 1989, the trial court heard evidence, including six experts called by the state and four experts called by the defense. Ultimately, the trial court denied the motion, concluding that the relevant scientific principles and techniques are valid and that the laboratory procedures in this case were performed in a scientifically acceptable manner, "thereby obtaining sufficiently reliable results within a reasonable degree of scientific certainty so as to be admissible in evidence."
The admissibility of DNA identification evidence is an issue of first impression in this court. 1 There are at present three private, for-profit laboratories equipped to conduct forensic DNA identification, two of which--Lifecodes and Cellmark--use essentially the same process. Lifecodes conducted the DNA tests in this case.
Considerable testimony was presented in this case about the methodology used by Lifecodes (which in many respects is standard in all DNA research--plant, animal or human), about its protocol and standards, and about its population statistics and probability calculations. The defendant's quarrel with DNA identification is not with the science on which it is based, nor with the general scientific acceptability of the techniques used to generate an "autoradiograph." The defendant's concerns essentially are Lifecodes' quality control, the manner in which it declares a "match," and in its probability calculations.
(a) It would be helpful at this point to review relevant principles of genetics and cellular biology. We set forth a "brief genetic and biological primer" from People v. Wesley, 140 Misc.2d 306, 533 N.Y.S.2d 643 (Co.Ct.1988):
A cell is the basic unit of all living organisms--including animals, plants, insects, and people. The human body has more than 10 trillion cells.
A cell has two main parts--the nucleus and the cytoplasm. The nucleus contains two important types of structures: chromosomes and nucleoli. The cytoplasm is all the material inside the cell membrane outside the nucleus.
The nucleus contains the cell's genetic program, a master plan that controls almost everything the cell does. It sends instructions to cytoplasm, which is the cell's chemical "factory," to take amino A chromosome is composed mainly of DNA and associated proteins and stores and transmits genetic information. In each human cell there are 46 chromosomes, arranged in pairs of 22 plus two sex chromosomes (represented by X for female and Y for male).
acids and build proteins--to construct an arm, a leg, a head, and ultimately a total, functioning human body.
DNA is an abbreviation for deoxyribonucleic acid, its chemical structure. It is a molecule that carries the body's genetic information. It is contained in every cell with a nucleus in every living organism.
In 1953, James Watson, an American scientist, and Francis Crick, a British scientist, working together at Cambridge University in England, discovered the chemical and spatial structure of the DNA molecule. It was a "double helix" in which two chains of nucleotides, running in opposite directions, are held together between pairs of bases reminiscent of the rungs of a ladder, and coiled like a spring. It looks like a twisted rope ladder or a spiral staircase. Wherever their derivation--human, animal or vegetable--all DNA molecules have this shape.
The long threads that make up the sides of the DNA ladder are made up of alternating units of phosphate and sugar called deoxyribose. The "rungs" of the "ladder" are made up of four compounds called bases. These bases are adenine, cytosine, guanine, and thymine (abbreviated A, C, G, and T). They are attached to the sugar units of the ladder's side pieces. Each rung consists of two bases: A-T, T-A, C-G, or G-C, held together by hydrogen bonds, a weak form of chemical bond. No other combination is possible because only the A-T and C-G pairs are chemically attracted to each other; that is, A can only link with T, and C can only link with G. (See Appendix for Figure 1.)
The order of the bases in one strand of the DNA ladder determines the order of the bases in the other strand. For example, if the bases in one strand of the ladder are ACTAGT, the bases in the opposite strand would be TGATCA.
Each rung on the DNA ladder is known as a "base sequence," or a "base pair," and constitutes a bit of information. There are approximately 3 billion bits of information, or base sequences, in a molecule of DNA--that is, the genetic code in the nucleus of each cell of the human body consists of approximately 3 billion bits of information. The DNA molecule is tightly coiled within the nucleus of a cell like a ball of yarn. Unraveled, a molecule of DNA is approximately six feet in length.
A sequence of three bases on the DNA molecule is known as a codon. Groups of codons form genes. A gene is a unit of inheritance composed of a segment of DNA and carrying coded information associated with a specific function. It contains a certain number of base pairs in a certain order. The instructions for making specific proteins from the 20 amino acids contained in a cell are carried by specific genes.
The genetic code lies in the order of the bases in the DNA molecule, organized in genes. This order of bases is passed on from one generation of cells to the next and from one generation of an organism to the next. It causes a rhinoceros to give birth to a rhinoceros and not to an ant.
Every human being inherits half of its genes from each of its parents. It is the order of the base sequences, organized in genes, that determines all of the characteristics of a living organism--the color of our eyes, the shape of our ears, and thousands of other traits. Within the DNA in the nucleus of every cell in the human body is all the genetic information needed to form another human body.
Each gene is a continuous segment of DNA along the molecule and is located at a specific site, known as a locus, upon a specific chromosome. Genes may be of different lengths and follow one another along the DNA molecule. Each gene differs from the next because the sequence of order of base pairs in one gene is not identical to the following one.
There is no restriction on which base pair must necessarily follow another. The only restriction is that an A base (adenine) on one strand of the DNA molecule must connect with, and only with, a T base (thymine) on the other strand, and a C base (cytosine) on one strand must connect with, and only with, a G base (guanine) on the other strand....
The discovery of the structure of DNA by Watson and Crick, recognized as one of the major scientific events of the Twentieth Century, caused an explosion in biochemistry, molecular biology and related sciences, and the technology thereof. Among its vast biological implications are mindboggling applications to medical diagnostics and forensic identification.
Now knowing the structure of DNA, and its immutable rules, and knowing that genetic information and instructions are transmitted by varying sequences of matched base pairs, molecular scientists were able to decipher much of the genetic codes. In 1970 there was isolated the first enzyme, known as a restriction endonuclease, or restriction enzyme, that cuts DNA molecules at specific sites. A flood of other restriction enzymes were thereafter identified and used to segment the strands of the DNA molecule....
Other major developments in DNA technology occurred, leading to enhanced methods of sequencing or fragmenting DNA and enabling the examination of specific fragment lengths of the DNA molecule.
DNA researchers were soon able to identify and map the location on the chromosomes of many genes and alleles (alternative forms of genes, as, for example, alternative genes that determine eye color pursuant to Mendelian rules of inheritance). Every two years a prestigious group of international scientists meets in a body known as the Human Gene Mapping Conference, receives applications for the acceptance, mapping, and publication of gene sites newly-discovered since the last meeting of said body. The Human Gene Mapping Conference, is uniformly recognized by the scientific community as the official registrar of gene sites....
The Human Gene Mapping Conference assigns a locus for every gene site accepted by it. A locus is the specific position occupied by a particular gene or alternative forms of a gene on a chromosome....
Long segments of DNA are the same from person to person. These are the genes whose functions are known to build the necessary organs that characterize the organism it controls--in a human being, a head, lungs, a heart, limbs, and the like. However, certain areas of the DNA are highly variable from one person to another. These areas are called polymorphisms.
These areas contain what is called "anonymous sequences" or "junk DNA" by reason of the fact that their function is not clearly understood.... Because of these polymorphic regions, the DNA from no two people, outside of identical twins, contains the same sequential pattern.
DNA ... forensic identification, involves essentially six steps, all the scientific principles and technology of which have gained general...
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