RIVERHEAD, N.Y., Sept. 29 - It was a moment three years in the making as the Long Island electrician accused of killing the Manhattan financier R. Theodore Ammon strode into court here, winked at his family and sat down with his lawyers, ready to begin his murder trial.
But in an incident that may cause a mistrial, the whole process halted. Before a packed courtroom, the Suffolk County prosecutor, Janet Albertson, stood up and said that the defendant, Daniel J. Pelosi, had been tape recorded making plans to intimidate and assault witnesses, tamper with the jury and threaten her children.
The accusations come from "hours and hours" of tape recordings of Mr. Pelosi at the Suffolk County jail, Ms. Albertson said. Mr. Pelosi has been jailed there since he was charged with murder in March.
Mr. Pelosi's lawyer, Gerald Shargel, leapt to his feet and called the allegations, made before jurors entered the courtroom, a desperate, last-minute tactic. The judge called the lawyers to his chambers and later postponed the case until Monday. Mr. Pelosi's mother walked out of the courtroom in tears. Reporters bolted to the lobby, using their cellphones.
It was a startling twist in a Hamptons murder case whose mix of sex, money, class distinctions and intrigue has drawn interest ever since Mr. Ammon failed to show up at work one morning in October 2001.