Forensics:                   

The Following Term Paper was prepared for a Forensics class I took at Durham Technical Community College. Circa 1992. I received a Grade of 4.0 for same.

THE FUTURE OF

DNA FINGERPRINTING

by

Jesse R. Duke

Introduction

The image that most of us have of the American courtroom is that of an arena of truth. When into this arena walks science, we often lean a little forward in our seats. We expect our hero to pull from his bag the proper weapon to shred the murky darkness and allow the truth to shine.

Recently, science has added a powerful new weapon to his bag of arms. This new gadget is known metaphorically as DNA fingerprinting (D f/p). D f/p has already been used in thousands of criminal cases since 1987.(1 Until recently, the use and impact of D f/p has met with little resistance. However, recent studies and friction within the scientific community have many sending up red flags. Also, the catcalls of criticism, for a multitude of reasons, signals a crisis in the works. Further, using the Frye "general acceptance" standard, recent use of D f/p as evidence has met with mixed results.(2 This suggest that Frye alone may not be adequate to deal with modern forensic issues.

In a sense, the current debate over D f/p is a microcosm of the present relationship of science to law. The resolution of this debate, and the correctness of current Frye standard interpretations will lay the cornerstone for the future of science in the courtroom.

At Issue

Ever since Watson and Crick first unraveled the mystery of the structure and function of the chemical we know as DNA, most of us have been satisfied with the simple knowledge that it is the blue-print of life, and self-replicates to allow living things to grow and reproduce. However, since that discovery, the place of DNA in science has rapidly gone from the pure science of knowing to aggressive application. In fact, "tool DNA" has been used for such diverse ends as fooling bacteria into making miracle drugs, to confirming a petrified leaf 18 million years old was indeed a magnolia leaf, to tracing human lineage to a single female "Eve" in ancient Africa.(3 One of the infant applications of DNA analysis is DNA fingerprinting. The notion that a small sample of tissue or body fluid contains an individual's DNA and that this DNA can be analyzed to provide evidence as to the individual of origin has instant and obvious application in forensics.

There are currently two techniques used to perform D f/p analysis. The first is restriction fragment length polymorphism or (RFLP). The use of RFLP rests on the knowledge that 99% of the 3.3 billion base pairs in human DNA are the same among all humans. Most of the remaining 33 million base pairs, that make-up the variant 1%, are what we normally think of as our gene traits (color, shape, and size etc.).(4 Unfortunately, extraction of these "genes" and their analysis is beyond our current ability. After you account for "genes", a small fraction of this 1% is regions of non-sense along the DNA strand. Known as core sequences, these areas repeat a pattern of base pair combinations over and over again like a "stuck phonograph". The number of repeats is highly variable for the total population. Thus, if you extract five or more of these segments from an individual's DNA, the chance of another person (other than an identical twin) having the same combination becomes astronomical. Cellmark Diagnostics, (a commercial company that provides D f/p services) claims the chance to be 1 in 30 billion.(5 The RFLP technique entails placing a drop of DNA core sequence extract in a gel and applying electrical voltage across it. The current pushes the segments Through the gel. In a given amount of time, small fragments (less repeats) are pushed farther than larger fragments. After development, what you have is a strip of film with dark bands where different sized fragments came to rest. In theory each individual's pattern of bands and their spacing is unique. Thus, the fingerprint of that person's DNA.(6 RFLP was adopted by the FBI in 1989 and is performed by two commercial companies in the U.S..(7

The other, newer, D f/p technique is polymerase chain reaction or (PCR). The principle behind PCR is not so different from that of RFLP- You still extract highly variable regions of DNA and graphically represent these differences as a unique pattern. PCR has great advantages over RFLP, and most feel it will eclipse RFLP in the future.(8 The big advantage of PCR is the small amount of DNA needed to get good results.

DNA can be thought of as a "twisted zipper" and each tooth, on one side, has a counterpart on the other side. The "trick" of DNA is that when it unzips and separates during mitosis, it is able to use "spare parts" floating in the medium to build the counter tooth. Thus, the whole missing side is rebuilt. This occurs for both halves of the zipper so we end up with two complete zippers. This process of unzipping and rebuilding in duplication is closely guarded in living creatures so that duplication only occurs as a cell is ready to divide and needs two sets of DNA to share. The power of PCR is that, in a test tube, we add plenty of spare parts, simulate conditions of mitosis, remove the regulating safe guard factors, and if into this environment we place a single strand of DNA ... we can have a billion fold replication in one afternoon.(9 This amplification of DNA is often very important to forensic investigation because biological crime scene evidence is often scant and in poor condition when it reaches the lab. To conduct RFLP analysis requires upwards of 500 nanograms (.0000005 grams) of DNA.(10 This is a fantastically small amount to try to contemplate. 1 gram equals about one fifth the weight of a nickel. This alone is a small weight by our everyday standards. Now picture a small bedroom 10ft. by 10ft. by 8 feet high filled completely with water. This represents 800 cubic feet of water. Now, one gram is to 500 nanograms as 800 cubic feet of water is to four tenths of an ounce. With PCR technology we can often get results with only 1 nanogram or one five hundredth of this amount.

Argument

Almost all concerned parties agree that D f/p, when properly applied, is a most valuable technique of individual identification. Victor A. McKusick chaired a two year NRC study of D f/p and recently commented that D f/p was a "valid means of convicting the guilty and freeing the innocent".(11 In addition, The much criticized position of Lifecodes(l of 2 major commercial interest in D f/p) that there is only a 1 in 10 billion chance of finding two identical sets of D f/p, has met with recent support from a Yale University study.(12

Yet, the future of D f/p is in no way certain and the disjunction of science to law, that D f/p has come to symbolize, has become a mass media circus. At the center of this cyclone lie the origins of D f/p. The technology of D f/p was developed in a vacuum. Scant little objective scientific study of D f/p has been published and almost no articles on the technique have appeared. This lack of information is due mainly to the motivations of the three principles that provide D f/p services (Cellmark Diagnostics, Lifecodes, and the FBI). Of these three, the first two are commercial outfits that have patented their own RFLP methods and regard raw data and data base information as trade secrets.(13 As for the FBI, it too is reluctant to publish or disclose raw data citing it's "privilege against self-criticism". Further, the FBI stands nearly alone in opposing independent proficiency testing.(14 This unwillingness to publish and submit to peer review is a breach of science methodology that extends back to Robert Hooke and the 1600's.

In addition, current standards of evidence allows novel forensic methods to be used without scientific verification.(15 The Frye standard uses an adversarial system that usually requires experts to take a side in a criminal case, and usually involves payment of the expert to maintain his side's position regardless. The objective is to help his side to victory.(16 The Frye standard stems from a 1923 ruling that allows admission of scientific evidence into the courtroom while the methodology is still somewhere between theory and full verification. Many have criticized Frye as being too vague and not restrictive enough. Often in doubt is what must be generally accepted ... theory, technique, or application? Also, who must accept it ... forensic science community, or the larger community, and is acceptance by consensus or a simple majority?(17 Considered against the backdrop of the buffet of non-scientific evidence admitted into court, Frye stands like a absurd monolith in the wilderness. Compared to the subjective reality of the human witness, D f/p even with warts seems crisp and clean.

Many have called for reform of both evidence standards, and D f/p technology. The loudest cries are for universal standards, lab certification, an end to trade secrets, more resources for both DNA insult and data base research, and better education and training of lab personnel.(18 Add to this list reexamination of the Frye standard and the development of PCR technology in the public domain.

Summation

The current status of DNA fingerprinting reminds me of a line from The Tale of Two Cities ... "it was the best of times, it was the worst of times ... ". When science drew from his bag of arms DNA fingerprinting, it laid open the relationship of science to law and the cancer of discourse has presented itself in fullness. How we proceed to rid ourselves of it's ugliness will make all the difference.

BIBLIOGRAPHY

Cherfas, Jeremy. "Ancient DNA: still busy after death" Science, 9-20-91, pp. 1354-1356 Notes: 3

Lampton, Christopher. DNA Fingerprinting Impact Books, New York 1991 Notes: 12, 16

Neufeld, Peter J. Colman, Neville. "When Science Takes the Witness Stand": Scientific American, 5-90 pp. 46-53 Notes: 1, 2, 4, 5, 13, 14, 15, 17

Reynolds, Rebecca. Sensabaugh, George. Edwards, Blake "Analysis of Genetic Markers in Forensic DNA Samples Using the Polymerase Chain Reaction" Analytical Chemistry, 1-1-91, pp. 2-15 Notes: 6, 7, 8, 9, 10, 18

,"Report Shows Genetic Fingerprinting To Be Reliable In Court": The Herald Sun, 4-14-92 p. A7 A.P. Wire Service Report, Washington, D.C. Notes: 11