DNA fingerprinting as a forensic identification tool in criminal investigations

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)

Conclusion

In conclusion, this essay was about DNA fingerprinting and how it has become a silent partner in the war on crime. Since the trial of the century, DNA evidence has become a household word. Although DNA fingerprinting is an expensive endeavor for crime enforcement, there is no doubt its accuracy outweighs cost restrictions. "Anything that an agency or police department would find forensically useful may cost as much as several thousand dollars to process, in addition to the fees associated with obtaining the expert witness testimony required by the court system." (Unknown) but, as technology and the Federal Bureau of Investigation reduce costs because of the DNA samples on record, this silent partner in the war on crime will continue to serve.