A study conducted by two criminologists at Texas State University has raised questions about the way high-profile crimes are investigated by the police. After reviewing the investigations of 50 crimes that resulted in a wrongful conviction, the research team discovered that detectives often became convinced that a person of interest was the perpetrator and abandoned all other avenues of inquiry. In many of these cases, investigators coerced confessions from suspects and ignored exculpatory evidence.
One of the wrongful convictions studied involved a man who was sent to prison in 1990 for the murder of a 15-year-old girl. The strongest evidence against the man was a confession that he later claimed was coerced. The case file reveals that detectives investigating the murder changed their theory of the crime when DNA evidence was discovered that exonerated their prime suspect. This evidence was subsequently instrumental in freeing the man after 16 years of imprisonment.
The study, which was published in the Northeastern University Law Review, concludes that conformation bias can lead to tunnel vison when detectives are under pressure from the media and their superiors to make an arrest. The results of this tunnel vision often include coerced confessions and ignored exculpatory evidence. This conclusion is backed up by data from the Innocence Project. About one in three of the people exonerated by the nonprofit group was wrongly convicted after confessing to a crime they did not commit.
Suspects in police custody usually make false confessions after being convinced by police officers that asking for an attorney would make their situations worse. Detectives say this because they know that the presence of an experienced criminal defense attorney would keep the interview on track and focused on facts rather than speculation. This is why attorneys would likely advise any person being interviewed about a serious crime to seek legal counsel before answering any questions.