PLYMOUTH, Mass.— AFTER more than 12 years in prison, convicted of raping children at his family's suburban Boston day care center despite his avowals of innocence, Gerald Amirault says he is pinning his hopes on new science to get him out.

Not on microbiology; not on DNA testing. No physical evidence of that sort exists against Mr. Amirault, his sister and their late mother. All three were convicted in 1986 and 1987 in the Fells Acres Day School case, which has become the longest-running of the highly publicized day care sexual abuse cases that swept the country back then.

Rather, Mr. Amirault is counting on the science of psychology. And judging by a blistering ruling this summer in his sister's legal battle, he may have a shot.

Those day care cases, it turns out, from the McMartin Preschool in California to Wee Care in New Jersey, set off an explosion of psychological research into the accuracy of children's memories and reporting of events.

In the last decade, researchers estimate, 500 studies have been conducted on children's ''suggestibility'' -- the extent to which suggestions implanted by adult interviewers can influence children's recollections and accounts.

Though debate still burns high on some points -- like the general level of children's accuracy and how resistant they are to disclosing that they have been abused -- researchers describe an emerging consensus over how children should be interviewed to minimize false reports.

Warring camps of psychologists also appear to have reached broad agreement on this basic picture: The vast majority of the tens of thousands of child sexual abuse accusations each year are true, and most children display a tremendous capacity to be accurate; but under certain conditions, if they are pushed and prodded in the wrong ways, children may say false things. And preschoolers of 3 and 4 tend to be more suggestible than older children.

It was that body of research that underlay the Massachusetts Superior Court ruling by Judge Isaac Borenstein in June that Mr. Amirault's sister, Cheryl Amirault LeFave, should be granted a new trial on her conviction of sexual abuse because of new scientific findings.

''Overzealous and inadequately trained investigators, perhaps unaware of the grave dangers of using improper interviewing and investigative techniques, questioned these children and their parents in a climate of panic, if not hysteria, creating a highly prejudicial and irreparable set of mistakes,'' the judge wrote. ''These grave errors led to the testimony of the children being forever tainted.''

Prosecutors maintain that the Amiraults got fair trials, and the state supreme court has repeatedly ruled against the family. But the court has never dealt with a lower court ruling like Judge Borenstein's.

Judges elsewhere, however, have previously cited suggestibility research in overturning a ruling made when it was all but given among clinicians -- based more on gut instinct than data -- that children would never lie about sexual abuse. The research played a role in a New Jersey appeals court's 1993 decision to free Margaret Kelly Michaels, who was convicted in 1988 in the Wee Care case, and has figured in other rulings and verdicts. The Michaels decision noted that ''certain questions planted sexual information in the children's minds.''

The developing consensus has been emerging in guidelines set by associations of psychiatrists, psychologists and other professionals who deal with accusations of child sexual abuse. Among the rules of thumb are these:

*Children should be interviewed in the most open-ended way possible at first, allowed to engage in ''free recall'' rather than responding to specific questions.

For example, in its 1997 guidelines for evaluating children who may have been abused, the American Academy of Child and Adolescent Psychiatry recommends that interviewers' initial questions should not be ''leading or suggestive and should be phrased in such a way that an inability to recall or lack of knowledge is acceptable. A leading question is, 'Uncle Joe touched your bottom, didn't he?' A suggestive question is: 'Did Uncle Joe touch your bottom?' ''

*The interviewers should be as unbiased as possible about whether abuse actually occurred, because studies have shown that interviewer bias can influence responses from children eager to please adults.

*No bribes, threats or peer pressure should be brought to bear on the children. There should be no ''Johnny told me. Why won't you?''

*The number of interviews, repetitious questions and leading questions should be kept to a minimum. Many communities around the country, including virtually every major city, have set up children's assessment centers over the last several years so that children who may have been abused can undergo one-stop interviews.

*Interviews should be carefully documented and preserved so the record can be checked for tainting.

*Children should not be encouraged to imagine acts that did not occur. Such imaginings, studies have shown, can sometimes be confused with real memories.