Until the middle of the 1980s, criminal investigators used to compare evidence collected from crime scenes to find the suspected offenders. This evidence usually consisted of fingerprints, teeth marks, hair, semen samples, blood, and fingernail scrapings. Fingerprints were considered by investigators the best lead for the identification of a suspect and for connecting the supposed criminal to the crime scene. Fingerprints are the unique markers of an individual, but they have limited value in crime detection because they can be altered through surgery (Greene, 2007). The uniqueness of such evidence as hair, teeth marks, blood, and semen is also subjective. In 1985, Sir Alec Jeffreys and associate Victoria Wilson successfully proved that in the DNA (deoxyribonucleic acid) of human beings various tracts that they called minisatellites repeat in core sequences of DNA. They discovered that these minisatellites are unique for each individual, except identical twins (Greene, 2007). DNA fingerprinting became a powerful technology that has changed the criminal justice practice of the modern world. The purpose of this work is to discuss the effectiveness of DNA fingerprinting as a tool in criminal justice practice.
The discovery of DNA fingerprinting was monumental for forensic criminologists. It became easier define a unique characteristic of an individual by having just a small amount of evidentiary samples from a crime scene that contain nucleated cells left by a perpetrator. Deoxyribonucleic acid (DNA) is a mixture of various chemicals that every cell of a person’s body has. It consists of 23 pairs of structures called chromosomes. Twenty-two pairs are referred as autosomes, which are morphologically similar. The twenty third pair is a set of sex chromosomes called X and Y. They determine the sex of an individual. These structures carry complete information of all characteristcs of an individual. Men have one X and one Y chromosome while women have two X chromosomes. Every chromosome is composed of two long strings of chemical elements, which are twisted together in a shape of a double spiral (Vij & Biswas, 2005). The chemical elements appear in pairs as rungs in this twisted chemical chain. The four chemical elements of the genetic code control the production of proteins by a cell, which allows the human body develop and function properly (Vij & Biswas, 2005).
The genetic code of each person, except identical twins, is unique. The string of chemical elements of an individual’s DNA is like a unique bar code. Each person inherits half of his or her DNA from his or her father and half from his or her mother. This fact also makes possible identification of one’s relatives. The closer the relatives are the more alike is their DNA sequence. This law of genetic inheritance makes DNA fingerprinting useful in identification of an individual.
People often leave some traces of their DNA at crime scenes. Deoxyribonucleic acid can be received from a piece of skin, hair roots, blood, saliva, semen, or even cells shed from a skin of an individual when he/she touches an object (Greene, 2007). Collected biological samples are analyzed in laboratories, where DNA is extracted and amplified by using a chemical reaction. The received data produces a string of numbers based on part of the sequence of chemical elements, which is called a DNA profile. These profiles are based on only some parts of the whole sequence of the DNA, which are called “short tandem repeats (STRs). The eventual DNA profile is composed of the number of repeats in every STRs and the results of a test on the sex of an individual (Greene, 2007).
Police agents have to submit crime scene DNA profiles for inclusion in the national DNA database CODIS through their regional or state crime labs. This program is maintained by the Federal Bureau of Investigation (FBI). When the match between evidentiary DNA and a DNA from the database is found, it is called “hit”. According to CODIS, there were 119,782 forensic files and 2,643,409 offender profiles placed in the National DNA Index System in November 2005. The FBI reported that the CODIS database has produced more than 25,900 hits in over than 27,800 investigations (Greene, 2007).
Nevertheless, the effectiveness of forensic evidence is dependent on the proper collection, storage, and analyzes of the evidence (Greene, 2007). According to FBI reports, the FBI Laboratory has a significant forensic DNA case backlog, and it is constantly increasing (Fine, 2011). For example, in March 2010, the FBI Laboratory had a backlog of 3,211 forensic DNA cases. As a result of that, the time that the Laboratory needs to return results can take over 600 days (Fine, 2011).
The problem is caused with the growing demand, lack of laboratories, and a modern laboratory informational management system (Fine, 2011). DNA testing faces some other problems such as impurity of samples, their improper collection, mixed samples can be difficult to identify correctly, some technical challenges, like errors in the hybridization and probing process, and the risk that the DNA Database can be hacked and misused by the criminal individuals (Greene, 2007).
Despite all possible disadvantages of using DNA fingerprinting in crimes solving, the power and importance of this technology is undeniable. Forensic DNA testing is improving day by day. Implementation of outsourcing agreements with public and private laboratories, made by the FBI Laboratory, helps to reduce the level of DNA case backlog. Many other aspects are improving daily in DNA technologies. All these improvements make the DNA fingerprinting system the most effective in the forensic science.