Watch John Oliver Call Out 'Bullshit' Forensic Science

'Last Week Tonight' host detailed how hair, bite mark, fingerprint, DNA analyses are "[not] as reliable as we've become accustomed to believe"

John Oliver called out "bullshit" forensic evidence on 'Last Week Tonight,' explaining how even fingerprint and DNA analysis is far from foolproof.

Forensic evidence may appear foolproof on flashy TV crime dramas, but as John Oliver detailed on Sunday's Last Week Tonight, these techniques often breed "bullshit" results in real life. "Prosecutors often complain about a so-called 'CSI effect,' where jurors expect to see forensic evidence in every case," the comedian said. "The problem is: Not all forensic science is as reliable as we've become accustomed to believe."

Numerous studies have called into question the validity of some forensic evidence. A 2016 Presidential Science Council report concluded that, "expert witnesses have often overstated the probative value of their evidence, going far beyond what the relevant science can justify." In particular, Oliver argued, "highly subjective and unreliable" techniques like hair and bite mark analysis have resulted in numerous "terrible convictions."

"Judges often rely on precedent to decide to what to allow in front of a jury," he said. "So if a particular discipline has been in court before, it is likely that a judge will admit it again. All of which means that decisions about the validity of science are being made by people who don't necessarily know much about it."

Peter Neufeld, co-founder of Innocence Project, stated in a video interview, "Historically, we had a situation where two scientifically illiterate lawyers argue the bonafides of scientific evidence before a scientifically illiterate judge so that 12 scientifically illiterate jurors could decide the weight of that evidence."

Oliver used a reliably goofy analogy to put this complex reality in perspective: "Trials can often be a situation where no one knows what they're doing," he said. "It's like a cooking competition for toddlers hosted by a stray cat and judged by goats."

Even more reliable means of analysis, like fingerprints and "the gold standard," DNA, are "by no means infallible." The FBI has discovered that fingerprint analysis could have a false-positive rate as high as 1 error in 306 cases, and particularly messy crime scenes can result in complicated DNA findings.

Oliver highlighted the progress of the National Commission on Forensic Science, established to advise the Justice Department on how to side-step faulty science. Only problem: Attorney General Jeff Sessions shut down the program in April. Sadly, the host noted, "we may honestly be actively going backwards on this issue."

To counter that regression, Oliver created a hilarious trailer for a fake TV drama, "CSI: Crime Scene Idiot," starring Josh Charles as a cocky detective who pairs bogus evidence (like bite marks on a bologna sandwich) with awful puns ("Now that's what I call 'dead meat'").