Turns out Peterson was called as a professional witness in a court case in 2013 and tried to use his "Big Five" personality test as evidence that the defendant wasn't guilty of manslaughter.
The defendant was a homosexual man who murdered another homosexual after he had sex with him then the guy say "I have HIV btw lol":
>The Crown alleged that after having sex with Stuart Mark (the deceased), and learning the deceased was HIV positive, the appellant killed the deceased in a rage. The key evidence against the appellant was his video-recorded confession to two police officers admitting to the crime.
Peterson claimed that his personality test proved that the confession the defendant gave was invalid, that it somehow proved he had a personality that was "susceptible to being manipulated", so the confession he gave to the police was invalid.
Here's what the judge had to say:
>The judge concluded that Dr. Peterson’s methodology about the appellant’s personality lacked a sufficient scientific basis and was unreliable. Dr. Peterson had never met the appellant, nor watched the confession and his opinion (at para. 45):
>[D]id not explain how the significance of these results on the reliability of [the appellant’s] confession or how the other traits identified by the test scores interrelated or informed the interpretation of the results. There was no explanation as to the legitimacy of isolating one personality trait from the others in determining a person’s response to interrogation.
In other words, Peterson's personality test, that he sells for $10 a pop to hundreds of thousands of people, has no scientific basis in reality, and when asked to defend his personality test and explain how it applies to something in the real world he came up with nothing.
The defendant was sentenced to 7 years for manslaughter.
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