MadSci Network: Medicine

Re: What is the importance of DNA fingerprinting in Forensic Science?

Date: Wed Mar 13 10:05:34 2002
Posted By: Dale L. Laux, Staff, Serology/DNA, Ohio Bureau of Criminal Identification
Area of science: Medicine
ID: 1007592505.Me


To answer your question simply, DNA typing has been called the most 
important discovery in forensic science since fingerprints.  It has 
revolutionized the analysis of body fluids left behind at crime scenes or 
found on subject's clothing.

Around the same time fingerprints were first being classified and used in 
criminal cases in the US, around 1900, a man named Karl Landsteiner 
dicovered that human blood coulkd be grouped into different types, which 
eventually became A, B, AB and O.  For 70 years, this was the only way to 
differentiate a blood sample left at a crime scene, etc.  Unfortunately, 
the discrimination rate was low; two random blood samples could be 
differentiated about 30% of the time using this system. 

In the mid 1970's, new technology allowed for the analysis of serum 
proteins by electrophoresis resulting in an improvement in the 
discrimination power, which now approached 90%.  

In the mid 1980's, a man named Alec Jeffries from England discovered that 
there were areas on DNA which were highly polymorphic (many forms) and 
people could be distinguished from each other to the point of uniqueness.

With today's technology, DNA typing using short tandem repeats (STRs)and 
capillary electrophoresis allows forensic scientists to analyze blood and 
other body fluids quickly and definitevely.  

Oh, and by the way, the very first time DNA was used in a criminal case, 
the suspect in the case was EXCLUDED as the donor of the stain.  
Throughout the years, DNA typing has allowed for the freeing of many 
innocent people, jailed for crimes they did not commit.

Hope this explains the importance of DNA typing in forensic science.

Dale L. Laux
Forensic Scientist

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