ROAD TOWN, British Virgin Islands (AP) —A potentially important witness will not be allowed to testify against four Americans accused of killing a Connecticut artist on Tortola, one of the British Virgin Islands.

Judge Kenneth Benjamin ruled that defendant Alexander Benedetto's attorney-client privilege extends to a conversation a private investigator hired by the victim's family allegedly overheard in Her Majesty's Prison in October.

Lois McMillen, 34, was found dead on a Tortola shore on Jan. 15, 2000. She had been vacationing on the island at the time. Benedetto and co-defendants Michael Spicer, William Labrador, and Evan George were charged with murder shortly afterwards and have been jailed since.

Luis Reveiz, a former FBI agent working for both the McMillens and prosecutor Terrence Williams, claims that Benedetto told one of his lawyers within Reveiz' earshot that someone had sex with Lois McMillen the night before her body was found. Reveiz said it was "apparent" to him that Benedetto was talking about co-defendant William Labrador. He informed Williams about the incident in a letter in October, which was reviewed by Court TV last week.

The investigator might have lent support to testimony from the prosecution's star witness, former Labrador cellmate Jeff Plante. He is expected to testify that Benedetto said Labrador had McMillen up at the defendants' house and accused him of having more complicity in the crime than the others.

But another prosecution witness did help their case on the stand Monday. A forensic expert from Britain said the suggestion that McMillen took her own life was "laughable." The defense has raised suicide as an alternate explanation for the artist's death.

Prosecutors have argued that one of the defendants held McMillen face down in shallow water until she drowned.

The four defendants, who have pleaded innocent, deny being with McMillen the night she died, although they said they shared drinks and food on the two previous evenings.

-Material from the Associated Press was used in this report