Prior to the 1980s, courts relied on witness testimony and eyewitness testimony as their primary source of evidence. Notoriously unreliable, these techniques have since disappeared to give way to the astonishing reliability of forensic DNA analysis. In 1984, British geneticist Alec Jeffreys from the University of Leicester discovered an interesting new marker in the human genome. Most DNA information is the same in every human being, but the unwanted code between genes is unique to each person. Junk DNA used for investigative purposes can be found in blood, saliva, sweat, sexual fluid, skin tissue, bone marrow, dental pulp, and hair follicles (Butler, 2011). By analyzing this unwanted code, Jeffreys discovered certain sequences of 10 to 100 base pairs repeated several times. These tandem repetitions are also the same for everyone, but the number of repetitions varies greatly. Before this discovery, a drop of blood at a crime scene could only reveal a person's blood type, plus a few proteins unique to certain people. Now, forensic DNA analysis can reveal a person's gender, race, susceptibility to disease, and even propensity for high aggression or substance abuse (Butler, 2011). Most importantly, the certainty of DNA evidence is extremely powerful in court. Amazed by the near-perfect accuracy of this technology, the FBI changed the name of its Serology Unit to the DNA Analysis Unit in 1988 when it began accepting requests for DNA comparisons (Using DNA to Solve Crimes, 2014). Thirteen standard tandem repeats are used in modern forensics, and together these sequences create a DNA profile. Except in the case of identical twins, the probability that two people have the same genetic code in the thirteen central loci is less than one in a trillion (Jones, 2004). Investigators compare these...... middle of paper ......d Beyond." Forensic Magazine. Web. May 29, 2015. http://www.forensicmag.com/article/dna-forensics-rflp- pcr -str-and-beyond (Fall 2004). “Using DNA to Solve Crimes.” United States Department of Justice: National Institute of Justice (September 9, 2014). /advancing-justice-through-dna-technology-using-dna-solve-crimesSachs, Jessica Snyder DNA AND A NEW KIND OF RACIAL PROFILING 2004http://www.popsci.com/scitech/article/2004-. dna-and-new-kind-racial-profilingH.M. Wallace, AR Jacksona, J. Gruberb, AD Thibedeaub Forensic DNA Databases – Ethical and Legal Standards, ScienceDirec, 2014. http://www.sciencedirect. com. /science/article/pii/S2090536X14000239Westphal, Sylvia Pagán DNA profiles link the drug to its source, 2003https://www.newscientist.com/article/dn3919-dna-profiles-link-dope-to-its-source./