Essay About Dna Profiles And Forensic Index

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Presumptive testing is cheap, rapid and often portable, and gives the first indication of
whether target substances might be present in a sample. The process can be heavily
automated, often using an immunoresponse in combination with fluorescence for
detection. It is not legally defensible, but is used to screen out negative results before
going on to confirmatory testing, which definitively identifies and measures the amount
of specific chemicals. Confirmatory testing is legally defensible but is usually time-
consuming, requires expert operation, and is not portable and also is kind of expensive.
CODIS generates investigative leads in crimes where biological evidence is recovered
from the crime scene using two indexes: the forensic and offender indexes. The
Forensic Index contains DNA profiles from crime scene evidence. The Offender Index
contains DNA profiles of individuals convicted of sex offenses (and other violent
crimes) with many states now expanding legislation to include other felonies. Matches
made among profiles in the Forensic Index can link crime scenes together; possibly
identifying serial offenders. Based on a match, police in multiple jurisdictions can
coordinate their respective investigations, and share the leads they developed
independently. Matches made between the Forensic and Offender indexes provide
investigators with the identity of the perpetrator(s). After CODIS identifies a potential
match, qualified DNA analysts in the laboratories contact each other to validate or
refute the match. DNA analysis methods allow much smaller trace samples to be used.