DNA- an Investigator\'s Silent Partner

DNA- An Investigator's Silent Partner

This essay is about DNA fingerprinting and how it has become a silent partner in the war on crime. The ever popular O.J. Simpson murder trial in the early 90's made DNA evidence another household concept. Since that trial, DNA evidence has become a common feature throughout American criminal trials and jurisprudence. "As a forensic tool, DNA analysis was initially used to link an already known suspect to a particular crime scene. In these situations, law enforcement officers obtain DNA from the suspect and compare it to DNA recovered from the crime scene." (Peterson) Direct analysis of known suspects DNA has become a very common forensic tool.

Today, the FBI and many other law enforcement agencies house individuals DNA samples in electronic databases. "Combining the results of several genetic systems as is done in DNA fingerprinting by the direct use of the product rule is based on an assumption of random mating, because it assumes that any profile of alleles at more than one locus occurs at random, that alleles at different loci even if initially found together in a subpopulation, will randomize over time." (Schacter 155) These databases carry both convicted and innocent individuals information and the objective is to create an efficient and universal acceptable DNA fingerprint process.

The norm in criminal investigation today is that if and when a crime occurs and DNA evidence is recovered, the police literally compare that sample against any and all previously obtained DNA fingerprints that are already in the database. There have been many inadvertent matches that have led to convictions but there have also been many innocent men released from custody once it was discovered that they could not have committed a crime for which they were convicted.

DNA Fingerprinting

The reason DNA is such an effective forensic identification tool requires insights into the DNA molecule. DNA fingerprinting has been distinguished as a very accurate methodology for identification. "Allozymes, DNA Fingerprinting, mitochondrial DNA (mtDNA), minisatellite, and microsatellite techniques shed light on population differentiation and genetic variability." (Caro 14) the fingerprinting concept is based on the same philosophy as the art of fingerprinting - each fingerprint is unique. DNA represents a two-stranded molecule and each strand is a polynucleotide composed of a (adenosine), T (thymidine), C (cytidine), and G (guanosine) residues.

These residues are polymerized by 'dehydration' synthesis in a unique linear chain of sequences. Modern science has clearly identified that nucleotide residue is complementary along double-stranded DNA molecules. Consider that adenosine or a forms two hydrogen-bonds with thymidine or T. Or cytidine or C. forms three hydrogen bonds with guanosine or G. Therefore, in the majority of situations, a two-stranded anti-parallel complementary DNA molecule is said to fold to create a helical structure similar to a spiral staircase. Because of this, DNA is often referred to as a "Double Helix."

The true significance of a strand of DNA is that it is sure to house all of the necessary information that is the blueprint or code for various aspect of the body that it represents. Consider that in the majority of organisms, genetics is established by the breeding of pairs of parents which results in an off-spring that has a combination of each of the parents' genetic codes. "Despite the power of molecular biology to examine the information coded for by DNA, we have to know where in the DNA to look to find information of relevance to particular phenomena." (Cantor & Smith, 1999)

Advantages and Developments

There are many advantages to utilizing DNA fingerprinting. "The need to identify an individual arises in criminal and non-criminal situations, including identification of the perpetrator or victim of a violent crime, the victim of a natural disaster or the biological father in a case of disputed paternity. The arguments raised in favor of the DNA fingerprint technique derive from its power to identify objectively in all of these situations and the stability of DNA when exposed to harsh environments." (Schacter 145)

The DNA database philosophy is one of the most important developments since the inception of the idea. "The FBI is developing a computerized bank of genetic profiles of convicted criminals, just as it maintains fingerprint files. It should prove helpful in solving some crimes. "This is a tremendous technology which can eliminate many questions, and it definitely deserves a prominent place in the forensic field. But the reality is that, like with some forms of health care, our technology has exceeded our ability to pay." (Unknown)