TAUNTON, Mass. - Christina Martin, accused of killing her live-in companion by putting a fatal dose of LSD in his Jell-O, was convicted yesterday of first-degree murder.

After 5 1/2 hours of deliberations, the 12-member Bristol Superior Court jury ruled that Martin, of Westport, Mass., put the hallucinogenic drug into Richard Alfredo's dessert on Jan. 21, 1990, and that it caused a fatal heart attack.

The jury rejected testimony by Martin's daughter, Teasha Pauline, 17, who claimed that she, not her mother, poisoned the Jell-O.

Martin, 42, whose conviction - pending appeal - means she will spend life in prison without parole, showed little emotion.

Pauline testified that she laced the Jell-O with LSD because Alfredo, 61, had sexually molested her. Martin said she became suspicious of her daughter's strange behavior after the drug began taking effect.

During the trial, the prosecution presented witnesses to help prove the allegation that Alfredo suffered a fatal heart attack after eating the Jell-O Martin laced because she thought she would inherit his money and property.

Alfredo was buried without an autopsy, but his body was exhumed when police suspected that he did not die of natural causes.

In February 1990, two days after last being interviewed by police, Martin and her children moved to Montreal, where Martin was arrested two months later.

Renee P. Dupuis, the assistant district attorney who prosecuted

the case, said the district attorney's office had yet to determine whether to bring charges against Pauline.