After 40 years, DNA tests trap serial killer

Caught at last: DeAngelo served in the US Navy during the Vietnam War.

Should police have access to DNA databases? Last month, detectives in California caught a serial killer by using DNA information on a genealogy website. Privacy advocates are disturbed.

Between 1974 and 1986, one man in California committed at least 12 murders, more than 50 rapes and over 100 burglaries. He was known as the Original Night Stalker and the Diamond Knot Killer, based on the knot he would tie when binding his victims.

When DNA tests revealed that all these crimes had been committed by one person, he became known simply as the Golden State Killer.

The killer’s unique genetic fingerprint sat in evidence storage for decades. For most of this time, it was effectively useless. Time after time, investigators and forensics experts ran into the same problem: a genetic fingerprint isn’t much good unless you know who it belongs to. He was not one of the millions of convicts and arrestees in the FBI’s national DNA database.

Two weeks ago, police announced that they had found the killer. They had tracked him through his family tree.

Police checked the stored DNA against a genealogy site called GEDmatch. These sites have databases filled with profiles of people who have volunteered their DNA in order to find relatives and track their ancestry.

The suspect was not on this database either. But one of his relatives was. The relative’s DNA partially matched evidence related to the serial killer. Through one genetic test, the list of suspects was narrowed down to one family.

Investigators then used normal police techniques to narrow it down to one man: Joseph James DeAngelo. Now 72, he is a retired police officer who lived close to many of the attacks.

Cases like this have gone horribly wrong in the past. In 2014, a man named Michael Usry was accused of a murder in Idaho Falls nearly 20 years after the event. He was interrogated by the FBI and spent a month under suspicion because the killer’s genetic code was similar to his father’s, whose DNA sample had been obtained by

But his father was one of many false positives that plague DNA testing.

Since then, has refused all law enforcement requests. Is it right for the police to use DNA databases?

The greater good?

This is deeply sinister, say some. Even though it may have worked in the case of the Golden State Killer, as Ellen Nakashima writes in The Washington Post, “it turns family members into genetic informants without their knowledge or consent”. The evidence is low quality and casts suspicion over too many innocent people.

Of course it is, say some. The angry reaction to this shows how easily victims are forgotten, especially at a time when digital privacy is the story of the moment. Writing in The Toronto Star, Heather Mallick points out: “If you gave away your privacy to Facebook for fun, you might find this a more noble cause.”

You Decide

  1. Would you want your DNA to be available to the police?
  2. Is the world becoming more in favour of privacy — or turning against it?


  1. Draw as much as you know of your own family tree.
  2. Write a short story about an investigation where the police have to use unusual means to catch a criminal.

Some People Say...

“Privacy is not something that I’m merely entitled to, it’s an absolute prerequisite.”

Marlon Brando

What do you think?

Q & A

What do we know?
Between 1974 and 1986, a spate of similar robberies, rapes and murders spread across California. Initially, it was thought that the crimes were not linked, but the same DNA was found at each crime scene. In the past few weeks, it has emerged that the culprit was Joseph James DeAngelo. Police found this out by matching his DNA with DNA from an ancestry website.
What do we not know?
Whether DNA testing will improve its accuracy. At present, searches look for DNA profiles that are similar to the perpetrator’s, but by no means identical. As Wired notes, it’s “a scattershot approach that yields many fruitless leads.” We also do not know whether some US states will follow Maryland and the District of Columbia in banning DNA searches in police investigations.

Word Watch

He first became known in the Sacramento area as the East Area Rapist, before moving to Southern California where his crimes escalated to murder. He is suspected to have begun as the Visalia Ransacker before moving to Sacramento. But this is based on circumstantial evidence, and there is currently no known direct link.
Deoxyribonucleic acid is the molecule that contains the genetic code of all organisms.
Golden State
California’s nickname can be traced back to the discovery of gold in 1848, and the fields of golden poppies that can be seen each spring throughout the state.
Every human being has a unique fingerprint that does not change over the course of their lives. This was first discovered by English scientist Sir Francis Galton, who went on to become famous — and notorious — for his work on eugenics.
Joseph James DeAngelo
He has been charged with two counts of murder. Due to California state law on pre-2017 rape cases, DeAngelo now cannot be charged for many of his earliest crimes.

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