"I never saw a similar case where a defendant was so obviously innocent," said Herbert A. Posner, a retired State Supreme Court justice who is following the case.

Yet the police and prosecutors in the case refuse to admit the possibility that they erred, or that the police detective’s deceptive tactics could have produced a false confession. The prosecutorial inability to say “I was wrong” is too common, and it may result in Tankleff spending the rest of his life in prison for a crime he didn’t commit.

Steven A. Drizin, legal director of the Center on Wrongful Convictions at Northwestern University, who studied the Tankleff case, said: "Unfortunately, in almost every wrongful conviction case, even when DNA excludes the suspect, law enforcement officers - whether blinded by tunnel vision, whether they don't want to admit a mistake, whether from fear of civil liability - they remain fixated on preserving a conviction, even in the face of compelling contrary evidence. That's the saddest thing in these cases."

Winning exoneration typically takes a decade and sometimes comes after the defendant dies in prison, said Samuel R. Gross, a University of Michigan law professor and co-author of a landmark study of 340 exonerations. He called them "the tip of an iceberg" of tens of thousands of such cases.

When, as here, there is no DNA evidence to provide nearly irrefutable evidence of innocence, police and prosecutors often become intransigent, and judges are too frequently unwilling to disturb a conviction. This is particularly true when the police claim that a suspect voluntarily confessed. Prosecutors (and juries) consider a confession to be the gold standard of proof. It isn’t.

[F]alse confessions are well documented. "You had cases 75 years ago where someone confessed to killing a missing person, then the supposed victim wanders into a saloon," said Peter J. Neufeld, co-founder of the Benjamin N. Cardozo School of Law's Innocence Project, which has helped to free 170 prisoners.

Today, DNA has disproved confessions, as in the Central Park jogger rape case. Reviewing DNA exonerations nationwide, Professor Gross, of the University of Michigan, found that one-fifth of the defendants had confessed.

False confessions often result from a police officer’s focus on extracting a confession from a suspect instead of performing a full investigation.

Another tactical misstep that leads to erroneous arrests, critics say, is when the police prematurely focus on one suspect and ignore other possibilities. "The man with the most to gain from the death of Marty's parents changes identities and flies to California - that should not have been dismissed," Professor Drizin said.

False confessions also result from police trickery, a practice that courts have too often endorsed, despite the obvious potential for error.

The use of trickery by the police in interrogations is a legal and common technique, but critics say it invites false admissions. In Suffolk County, the State Investigation Commission found ineptitude, corruption and dubious confessions in a majority of cases in the 1980's.

The linked article on Tenkleff’s case is lengthy but well worth reading. The case is a microcosm of the various circumstances that lead to false confessions and wrongful convictions.