DNA: THE NEW FINGERPRINTS (9-2004)

In the days before modern forensic techniques, the accused 
were often convicted with nothing but circumstantial 
evidence or hearsay. Then came fingerprinting. It was a 
breakthrough in law enforcement because no two people have 
identical fingerprints.

Since then, there have been other methods discovered that 
can identify a person. Handwriting is also unique, although 
there is much more room for error. Voice prints and retinal 
scans can also be used to identify someone, but these last 
two require the use of electronic equipment. With 
fingerprints, all you need is some tape, dusting agent, and 
a magnifying glass.

But 20 years ago, a professor of genetics in England, Alec 
Jeffreys, serendipitously discovered the ultimate in 
identification techniques. Dubbed DNA fingerprinting, it 
has nothing to do with the fingers. Instead, the genetic 
material of the chromosomes, DNA, is extracted from any 
cell in the body, or cells left behind at a crime scene. 
The DNA sequences are then compared to see if they match 
the person being identified. 

For criminal suspects, it means fairly definitive proof 
that they either did or did not commit the crime. That is 
why DNA fingerprinting is so widely used these days.

Jeffreys remains awed by the technique. But he does have 
some concerns.

When he first developed the DNA test, he used dozens of 
markers. Markers are DNA sequences that are unique to each 
individual. Modern lab analyses use fewer markers for 
identification. Even so, the risk of making a false match 
is less than a billion to one.

The problem, according to Jeffreys, is that when DNA 
databases kept by law enforcement agencies become huge, the 
odds of at least one false match become more likely. For 
example, Britain keeps a database of 2.5 million DNA 
fingerprints. The odds of a false match in that database 
are one in 400.

Another worry for Jeffreys is that DNA databases may be 
open to abuse by those who would seek to invade someone’s 
privacy. It might be possible to weed out medical 
information, ethnicity, and other information about a 
person from their DNA samples. 

But with proper safeguards in place, a national DNA 
database would make it much easier to find criminals and 
bring them to justice. The FBI currently keeps a 
fingerprint database. A DNA database comprising samples 
from everyone in the country would be of tremendous value 
in criminal investigations. But, again, safeguards would 
need to be in place to protect privacy.

DNA fingerprinting can be used for more than just helping 
to identify a murderer or a rapist. The first year the 
technique was discovered, it was used in an immigration 
case to prove that a boy really was his parents’ son. 

The technique was also used to prove that Dolly, the first 
cloned sheep, was really a clone.

Last Friday marked the twentieth anniversary of the 
discovery of DNA fingerprinting. In that time, it has been 
used to prove countless paternity cases, to convict scores 
of murderers and rapists, to help identify missing persons, 
and to exonerate several innocent persons who had been 
previously convicted of rape. 

In 1994, Jeffreys was knighted. Thanks to him, it is now 
much easier to identify who the real criminals are.