Forensics DNA Testing
The use of DNA fingerprinting to solve crimes began in Leicester, England, in 1987, where the technique had been discovered three years earlier. Since then, its use has become widespread.
These days, many national and international databases include the DNA of known or suspected criminals and DNA is used for identification within some of the military services. So what is genetic fingerprinting and how can genetic fingerprinting identify a person? To explain this, you'll first need to know about DNA.
Defining DNA
DNA (deoxyribonucleic acid) is the genetic material that composes all human beings' systems. You could say that it’s our blueprint. DNA is made up of four nucleotides (adenine, cytosine, guanine and thymine) which combine in base pairs. Most of our DNA is identical; however, about 0.1 per cent of our genetic material is unique to us and this is the material that can be used in DNA genetic fingerprinting to solve crimes.
DNA Samples and Genetic Fingerprinting
In order to get started with DNA fingerprinting, testers need a DNA sample from blood, saliva, hair, fingernails, teeth, semen or other tissue or bodily fluids. This is then analyzed to form a DNA profile or fingerprint.
In the early days of DNA testing, a method known as RFLP (restriction fragment length polymorphism) testing was used. This required large samples and was time-consuming, so it was replaced by PCR (polymerase chain reaction) analysis, which was faster and more accurate.
Today, the most widely used analysis method utilizes short tandem repeats (STR). It is based on PCR. These test 13 core DNA regions (called loci) of a person’s genome to build up a profile. The more matches there are, the more likely it is that you have identified the right person.
Using DNA Profiles
Genetic fingerprinting and forensics are now key crime fighting tools. DNA profiles can be used to exclude suspects from consideration or to prove categorically that they were there. If law enforcement officials have DNA samples, they can compare this against the FBI’s Combined DNA Index System (CODIS). Some states enforce criminal DNA testing, which means that known offenders’ profiles become part of the database. This also applies to sex offenders across the 50 states.
Most states have laws that require convicted felons to submit DNA samples and many states require those arrested to submit samples on request. One example of such a law is Katie’s Bill, passed in New Mexico in 2006. This law requires the police to take DNA samples from those arrested for crimes. It is named after Katie Seppich, whose 2003 murder was solved after her murderer was convicted of another crime in 2005.
Moral Issues with DNA Fingerprinting
The use of genetic fingerprinting raises many moral and legal issues. In particular, many people feel concerned that our Fourth Amendment rights may be violated. Others worry that people’s genetic material may remain on file even if they are not convicted or a conviction is later overturned.
Meanwhile, the issue of DNA testing of inmates has resurfaced. With recent cases where inmates on death row used DNA evidence to overturn their convictions, many feel that inmates sentenced to death should be tested to prove or disprove their guilt. At more than $1,000 per test, the cost of this testing is also an issue.
Despite these issues, DNA testing continues to be widely used by law enforcement officials around the world. Testing is becoming more reliable and although the possibility of error still exists, the use of genetic fingerprinting as part of a suite of evidence makes it a useful tool in securing criminal convictions.
Resources
ACLU (2002). DNA And The Death Penalty. Retrieved August 27, 2008, from the ACLU Web site: http://www.aclu.org/capital/innocence/10392pub20020626.html.
Human Genome Program (2008). DNA Forensics. Retrieved August 27, 2008, from the Human Genome Project Information Web site: http://www.ornl.gov/sci/techresources/
Human_Genome/elsi/forensics.shtml#6.
HowStuffWorks (2001). How DNA Evidence Works. Retrieved August 27, 2008, from the HowStuffWorks Web site: http://science.howstuffworks.com/dna-evidence.htm/printable.
Lawless, Jill (2004). DNA Fingerprinting Sparks Fresh Worries. Retrieved August 27, 2008, from the MSNBC Web site: http://www.msnbc.msn.com/id/5944270/.
Net Industries (2008). Genetic Fingerprinting As A Forensic Tool. Retrieved August 27, 2008, from the Net Industries Web site: http://science.jrank.org/pages/2129/DNA-Fingerprinting-Genetic-fingerprinting-forensic-tool.html.
Rosner, Dalya (2004). How Does DNA Fingerprinting Work? Retrieved August 27, 2008, from the Naked Scientists Web site: http://www.thenakedscientists.com/HTML/
articles/article/dalyacolumn8.htm/.
About Us