Forensic Scientist Reveals Disturbing Error Rates in DNA Database Matches

The National Offender database, which contains the DNA profiles
of offenders, has more than 13 million profiles, almost double
since 2009. However, there is growing concern about the accuracy
of DNA matches and the potential for human error in the system.
Forensic scientist and professor Dan Krane revealed alarming
error rates in DNA test results on the "Hidden Killers" podcast
with Tony Brueski.
 
 Krane, who has extensive experience working with DNA
databases, expressed his excitement about the potential to
identify error rates or determine errors in DNA test results. He
cited his involvement in an investigation for the state of
Victoria in Australia, where he had access to about 15,000 DNA
profiles. "When you did all possible pairwise comparisons of
those 15,000 people, what you found is that there were a fair
number that matched perfectly at 14 out of 18," Krane explained.
"There were fewer that matched at 15 out of 18, but still some,
fewer that matched at 16 out of 18, but still some, and then a
whole bunch that matched at 17 out of 18, more than matched at 14
out of 18, and then a whole bunch that matched at 18 out of
18."
 
 Krane explained that the only explanation for the ones that
matched at 18 out of 18 was that these were people who were
entered into the system twice, possibly under an alias. However,
the ones that matched at 17 out of 18 indicated that there was a
mistake in one of the two times their DNA got entered into the
system. This translated into an error rate of one in 300. "And
when you're talking about chances of a coincidental match in the
quintillions or the bazillions, if you prefer, yet you make a
mistake every 300th time that you try to generate a DNA profile,
the bazillion number doesn't matter anymore. It gets swapped out
by that chance of making a mistake," Krane said.
 
 This error rate is particularly concerning as it means that
opportunities to generate useful investigative leads are missed.
If a DNA sample is collected from a crime scene and there is no
suspect, authorities search the CODIS database to find a match.
However, every 300th time this is done, a lead is not generated,
which Krane believes is an unacceptably high failure rate given
the consequences of having a rapist or a murderer go without
being apprehended.
 
 Krane suggested that one way to correct this could be by
doing a pairwise comparison of the 13 million profiles in the
federal database to determine if errors happen more frequently at
one of the locations than others. "Maybe one of those loci just
is more error-prone than others. Maybe the biology just doesn't
work as well for that one locus. That one location. And when you
do your database search, maybe you don't include that one, right?
Or maybe you include it and this, but you factor in that you
discount it because that one is just more prone to having a
mistake," Krane suggested.
 
 Krane also expressed concern about the secrecy surrounding
the CODIS database and suggested that more people in the correct
positions should have access to it to identify more criminals and
solve more cases. He also mentioned the development of
probabilistic genotyping systems, expert systems used to
interpret test results that human analysts find too complicated.
These systems, while not openly shared due to stringent
non-disclosure agreements, can distinguish between signal and
noise, which is particularly useful when dealing with a small
amount of DNA or a sample with many different contributors.
 
 While the expert systems may not explicitly use artificial
intelligence (AI), they involve serious computer science
undertakings with hundreds of thousands of lines of computer
code. These systems may help reduce human error and improve the
accuracy of DNA database searches, ultimately helping to catch
more criminals and solve more cases.
 
 Krane's insights highlight the need for more transparency
and improvement in the system to ensure that DNA databases are
used to their fullest potential in solving crimes and catching
criminals.
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