DNA is the hereditary material present in nearly all
human cells and the cells of almost all other life forms.
Composed of four nucleobases (biological compounds) in
various sequences, it builds and maintains organisms —
similar to the way letters of the alphabet are arranged to
form words and sentences — and our understanding of it has
come a long way since it was discovered in the 19th century.
The DNA molecule was initially isolated in 1869 by Swiss
chemist Johann Friedrich Miescher, but it was University of
Cambridge biologists Francis Crick and James Watson who
first proposed the double-helix structure of DNA, in a 1953
issue of Nature. A few decades later, British geneticist Sir
Alec Jeffreys made a breakthrough discovery that led him to
develop DNA profiling. That technology came into wider use
in 1986 and immediately helped authorities convict a man
of two rapes and murders committed within the past three
years. Anyone who’s watched CSI, Forensic Files or any other
police procedural TV show in the past two decades has heard
of the process, also known as DNA fingerprinting, and for
criminal investigators it’s now the gold standard for ascertain-
ing innocence or guilt. Forensic experts extract DNA at crime
scenes from samples of skin cells, blood, semen, saliva or other
bodily fluids; the processed samples are then compared with
those of a suspect, in the hope of getting a match and identi-
fying the bad guy. (Of course, while the turnaround time is
seemingly instant on CSI, real-world lab results can take days
or weeks or the tests may never be processed at all.)
Conversely, DNA has also played an integral part in
freeing people who have been wrongfully imprisoned. The
Innocence Project, a nonprofit legal organization, uses the
testing to exonerate innocent inmates serving sentences. To
date, 350 people have been released thanks to those efforts.
n April 24, 2018, 72-year-old Joseph James
DeAngelo, now known as the Golden State Killer, was apprehended and eventually
charged with 13 counts of murder and 13 counts of attempted kidnapping, thanks to
publicly shared genetic codes. No, DeAngelo didn’t submit a sample to find out what
percentage Italian he was, but a distant relative of his did take an at-home genetic test.
Using a crowdsourced online database, investigators found that the test taker’s
DNA partially matched DNA taken from evidence related to the serial killer. From
there, the search was narrowed from a pool of millions down to a single family, even-
tually leading police to DeAngelo, who lived within miles of many of the attacks.
This was the second time that law enforcement used this method to catch a perpe-
trator, and in the short amount of time since, at least 13 other suspected criminals
have been identified in the same way. So even if you’ve personally never supplied
your own DNA to an outside party, if your relatives have, this information can be
used in a case involving you.