Richard Lapointe, convicted of murdering his wife's 88-year-old grandmother 18 years ago, had to have committed the brutal, messy crime in a window of as little as 20 minutes.

Lapointe's lawyer, in aggressive questioning of a former Manchester police detective, spent the morning Tuesday trying to undermine this essential element state's case against the mentally disabled man.

Lapointe is seeking a new trial, charging that police suppressed evidence in the case.

In the process, Paul Casteleiro appeared to damage the credibility of Michael Morrissey, the Manchester police officer who interogated both Lapointe and his wife in the aftermath of the murder of Bernice Martin. Morrissey was forced to admit he mispresented facts, withheld information and ignored basic interogation procedure in order to get a confession from Lapointe.

Casteleiro took sharp aim at the scenario that has Lapointe taking his dog for a 20-minute walk and killing Martin before returning home looking as if nothing had happened.

"You think someone could walk .. to Bermice Martin's house, murder her, stab her, blood all of the bedroom, rape her ... set her house on fire ....and it appears there would be no sign whatsover?" Casteleiro demanded of Morrissey.

"It's possible,'' Morrissey said. And later, he added, "my goal has always been through my entire career in law enforcement was to get to the truth."

Casteleiro, in a wide-ranging cross-examination of Morrissey that Judge John J. Nazzaro did little to reign in, repeatedly asserted that local police were out to squeeze a confession out of Lapointe -- no matter what the facts might suggest.