We've Been Using The Wrong Science In Court For 50 years

(dramatic music) - A man has been found lying dead at the side of the road with oozing, elongated wounds to his back.

To solve the murder, a local official calls all the farmers in the village and demands they all bring their tools to the main square.

In the square, each man is set to lay down his sickle. And then something curious starts to happen.

In the rising heat of the morning, flies begin to descend, all landing on a single sickle. Its owner buckles, falling to his knees and admits to murder.

This is from a 1247 book, "The Washing Away of Wrongs" by Song Ci. And it's the first writing we have of an empirical approach to forensics.

But okay, big deal. Anyone could have just swapped the sickles or used their neighbor's. But forensics today are much more accurate, right?

Fingerprints support investigations in over 70% of murders and DNA evidence in more than 90%. But then you also read an article like "Hair sample that put men into prison for 28 years, turned out to be dog hair."

- That is not science. That is not justice. - See, in 2009, the National Academy of Sciences published this 350 page report stating that, with the exception of nuclear DNA analysis, no forensic method has been rigorously shown to consistently demonstrate a connection between evidence and a specific individual.

And they also said that some tests do not meet the fundamental requirements of science. So we ask people to rank five famous forensic techniques, all of which are still being used in court.

Okay, five forensic techniques here. And I just need you to rank them in order of accuracy from the least accurate down here to the most accurate.

So what do you think? - I don't know if I'm gonna nail these. - Whoa. I dunno. - I don't know what forensic to put first here.

- Okay, hair. What are you thinking? - I think hair is last, eh? - I would probably put the hair on the top two.