SEVERAL months after Antonio Ramirez was shot seven times in Oakland, Calif., the police picked up a frightened 16-year-old named Felix, isolated him in an interrogation room late at night without a lawyer, rejected his pleas to see his mother, and harangued him until he began to tell them what he thought they wanted to hear.

They wanted a diagram of the crime scene, he later told his court-appointed lawyer, Richard Foxall, but whatever he drew was so inaccurate that the police never produced it. When he described escaping in one direction after the killing, they corrected him, because they knew from witnesses that the shooter had gone the opposite way. When he didn’t mention an alley nearby, they told him about it, and he incorporated it into his statement. “Now we’re getting somewhere,” said one officer, as Felix recalled to his lawyer.

So, they demanded, where was the gun? Felix denied having a gun. “That’s when they really got out of control and started yelling at him,” Mr. Foxall said. “He started to feel personally threatened.” Slyly, he made up something demonstrably untrue: that he had left the gun with his grandfather. “I thought this was brilliant,” his lawyer said, because it discredited the tale. “He doesn’t have a grandfather. Both grandfathers are dead.”

Once the police had badgered a rough murder confession from Felix, they taped it. Yet the confession lacked a critical detail — one that officers neglected to feed to him. Felix learned it three days later in court when he was handed the charge sheet and saw the date of the crime. He stared at the document and realized that he had the perfect alibi: On the day that Antonio Ramirez was gunned down, Felix had been locked up in a juvenile detention facility for violating probation in a case of theft.

The murder charge was dropped, of course, and Mr. Foxall was greatly relieved. “I would have hated to have had to try the case,” he said. “It would have been very scary. Juries don’t want to believe that somebody will confess to a crime he didn’t commit.” Judges don’t want to believe this either. In fact, according to Mr. Foxall, the juvenile commissioner in Felix’s case said, “Well, I don’t understand — why would he confess?”

If you have never been tortured, or locked up and verbally threatened, you may find it hard to believe that anyone would confess to something he had not done. Intuition holds that the innocent do not make false confessions. What on earth could be the motive? To stop the abuse? To curry favor with the interrogator? To follow some fragile thread of imaginary hope that cooperation will bring freedom?

Yes, all of the above. Psychological studies of confessions that have proved false show an overrepresentation of children, the mentally ill and mentally retarded, and suspects who are drunk or high. They are susceptible to suggestion, eager to please authority figures, disconnected from reality or unable to defer gratification. Children often think, as Felix did, that they will be jailed if they keep up their denials and will get to go home if they go along with interrogators. Mature adults of normal intelligence have also confessed falsely after being manipulated.

False confessions have figured in 24 percent of the approximately 289 convictions reversed by DNA evidence, according to the Innocence Project. Considering that DNA is available in just a fraction of all crimes, a much larger universe of erroneous convictions — and false confessions — surely exists.

Officers are taught to use all the tricks and lies that courts permit within the scope of the Fifth Amendment’s shield against self-incrimination. John E. Reid & Associates, which has trained thousands of interrogators, suggests that a suspect be induced to waive his constitutional rights to silence and counsel by giving him the famous Miranda warning “casually” and not immediately after arrest, when he is “defensive and guarded” and “more likely to invoke his rights.” When a skilled questioner splices it nonchalantly into conversation, the warning’s empowering message of choice can be lost on a suspect. Many false confessors have been routinely Mirandized in this perfunctory manner.

To get people talking, the Reid training also recommends questions that imply leniency without making explicit promises, and that reduce moral responsibility by blaming peer pressure: “Was this your idea or did your buddies talk you into it?” Interrogators are advised to pretend to have evidence but not to fabricate it. A suspect can be shown a card bearing a latent fingerprint and be told: “This is your fingerprint. We found it inside that stolen car.” That’s been allowed by courts if the police officer puts his or her own print on the card but not if the officer fakes it with the suspect’s print. Admissions produced by these tactics may be true or untrue.

A cunning lie generated a false confession from Martin Tankleff, 17, who found his parents one morning in their Long Island home slashed and stabbed, his mother dead, his father barely alive. The boy called 911 and was taken for questioning. Getting nowhere, Detective K. James McCready decided on a trick. He walked to an adjacent room within hearing distance, dialed an extension on the next desk, picked up the phone and faked a conversation with an imaginary officer at the hospital. He went back to the son and told him that his father had come out of his coma and said, “Marty, you did it.” In fact, Seymour Tankleff never regained consciousness and died a month later.

In experiments and in interrogation rooms, adults who are told convincing fictions have become susceptible to memories of things that never happened. Rejecting their own recollections through what psychologists call “memory distrust syndrome,” they are tricked by phony evidence into accepting their own fabrications of guilt — an “internalized false confession.”

That is what happened to a shaken Martin Tankleff, and although he quickly recanted, as if coming out of a spell, he was convicted and drew 50 years to life. He spent 17 years in prison before winning an appeal based on new evidence that pointed to three ex-convicts. But they have never been tried. Whoever killed the Tankleffs remains at large.

There are possible remedies. After Felix’s false confession, the Oakland Police Department began video recording “as soon as a homicide suspect enters the interview room, as opposed to only taping a portion of the interview,” said Sgt. Chris Bolton, the police chief of staff. Some lawyers worry nonetheless that judges won’t watch hours of subtle coercion, and that jurors will still find the taped confession decisive.

The police could be prohibited from lying about nonexistent evidence; from inducing a suspect to imagine leniency; from questioning minors without a parent or a lawyer present. They could be required to corroborate a confession with stringent evidence.

Finally, post-conviction challenges of confessions could be assigned to judges and prosecutors other than those who tried the original cases. The natural unwillingness to admit a grave error should not have to be overcome for justice to be done.