Can You Trust The Police?

The Maine Supreme Judicial Court issued an interesting decision this week that, ironically, involved lie detectors.  To briefly summarize, a criminal suspect was given a four-hour polygraph test, which he was told was "foolproof."  After the exam, the police told the suspect that he had failed the polygraph test, and they then tried (successfully, it turned out) to elicit a confession.

Not only is a polygraph test not "foolproof," it is in fact so unreliable that polygraph test results, and a defendants willingness or unwillingness to take a polygraph test are inadmissible in Maine courts.  The defendant in this case did not know this, but the police did.  They lied to the defendant, in order to trick him into confessing.

Up to a point, the courts tolerate lying by the police. In this case, Justice Levy and Justice Alexander wrote a concurring opinion reminding the police and the prosecutors that "the Constitution's tolerance for the use of deception as an investigatory tactic by the police is not boundless."  If trickery is used to coerce a confession, then that confession is not voluntary--one of the requirements for the admissability of a confession.  But, as a general matter, the fact that the police lied to a defendant to elicit evidence will not protect a defendant from having that evidence used in court.

But there is a larger issue: lying by the police may lead to a guilty person going to jail, but over the long term lying erodes public trust.  Claiming that polygraph tests are "foolproof" may seem like a small lie, but small lies add up.  At some point, the harm done to the public's ability to trust the police will outweigh the societal benefit of locking up one more criminal.  Have we reached that point?