By ANTHONY CASTELLANO and MARIA NIKIAS

U.S. Open tennis referee Lois Goodman, charged with killing her husband with a coffee cup several months ago, has passed a lie detector test, according to her defense lawyers.

"The results of the polygraph (lie-detector) test prove what we have said all along - Lois Goodman is innocent," Alison Triessl, an attorney for Goodman, said in a statement.

Goodman, 70, was charged with her husband's death on Aug. 21. Goodman's defense argues that he died from a freak accident.

"No one can challenge these results. The test was given by the most-respected FBI-trained expert in the country - Jack Trimarco," she said.

Goodman took the test during the first week of this month. Trimarco concluded there was "no deception" by Goodman.

On April 17, Goodman called police and told officers she arrived home and found her husband, Alan Goodman, 80, dead at the bottom of the stairs, said Lt. David Storaker, the chief of detectives at the LAPD's Topanga station.

"She surmised that he must have had a heart attack and fallen down the stairs," Storaker told ABCNews.com earlier this year.

Officers concluded that there was no sign of forced entry, and the statements Goodman was making seemed suspicious, so they investigated further, Storaker said.

On Aug. 2, the Los Angeles Country Coroner ruled the man's death a homicide.

The cause of death was multiple injuries to the head, Storaker said. According to the arrest warrant, he was killed with a coffee cup.

Although LAPD detectives said they think they know the motive, Storaker said they weren't sharing it because it will affect the case.

"We're trying to retrace the steps of both Goodmans that day to see if there was any strain in their relationship or arguments occurred," he said. "We don't want to taint any other memories."

Court documents obtained by ABC News earlier this year say that the tennis referee sent emails to another man that reportedly mentioned "terminating a relationship."

The documents, including a police detective's affidavit, also allege that the emails that Lois Goodman sent to the man talked about having "alternative sleeping arrangements," according to the Los Angeles Times. Goodman was annoyed that her husband of 50 years was calling 15 times a day, according to the New York Daily News, quoting a source.

"She's anxious to defend herself," said her lawyer in New York, Guy Oksenhendler. "My concern is that their actions may prejudice her defense in California."

If convicted, Goodman could face life in state prison, according to the L.A .County District Attorney's office. Prosecutors recommended bail at $1 million.

ABC News' Sydney Lupkin contributed to this report.