Claus Von Bulow denied Tuesday that he sent threatening letters to his former girlfriend, Alexandra Isles, after she testified against him in his first trial in 1982.

"I have not communicated with Mrs. Isles either directly or indirectly since the first trial," Von Bulow said outside the courtroom.

Danish socialite-financier Von Bulow, 58, is charged with twice trying to kill his wife, heiress Martha (Sunny) Von Bulow, in 1979 and 1980.

Lt. John Reise, the state police detective who has investigated the case since early 1981, said New York magazine theater critic John Simon, a longtime friend of Isles, told him that one reason Isles did not want to testify again was that she had received threatening letters after her first appearance.

Reise said Simon told him about the letters during a telephone conversation last week. Simon declined to tell Reise or anyone else where the former soap opera actress is hiding.

"Sometimes she's in Ireland. Sometimes she's elsewhere," Simon said.

The issue of Isles' whereabouts has become central to the retrial. Jurors in the first trial said her testimony helped them convict Von Bulow. Isles provided an alleged motive by testifying that she gave Von Bulow an ultimatum to divorce his wife.