NEW BRUNSWICK, N.J. — Suggesting that Melanie McGuire's extramarital affair was no motive to murder her husband, her defense called as a witness Wednesday a woman who had a one-night stand with the victim.

The witness, Elizabeth LaBlue, testified that she and William McGuire, colleagues on a work project, spent the night together in her hotel room after drinking margaritas. She said the liaison occurred two years before his death and never turned into a relationship.

"I asked him not to contact me anymore and I recommended that he and his wife seek marriage counseling," recalled LaBlue, an employee of a technology company in Tennessee. (VIDEO)

McGuire's defense maintains the fertility clinic nurse and her husband had a marriage "permeated with extramarital affairs" and that, in that context, her own two-year relationship with her physician boss, Dr. Bradley Miller, was not a reason to kill.

LaBlue, who was subpoenaed by the defense, appeared nervous and upset as she testified. She hung her head during one brief break in testimony and, when she was excused, she rushed to the restroom and broke into tears.

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She said her strictly professional relationship with McGuire began to change on the final day of her trip to New Jersey, when they spent time shopping and sightseeing together.

"After dinner, where did you and Mr. McGuire go?" defense attorney Joe Tacopina asked.

"Back to my hotel," LaBlue replied.

"Back at the hotel, did you have sexual relations with Mr. McGuire?" the lawyer asked.

"Yes, sir, I did," she replied.

On cross-examination, a prosecutor noted that William McGuire had discussed his marriage with her and even showed her a photo of his two sons, one of whom was a newborn. She said at one point in the afternoon they spent together, he took her to a jewelry shop and showed her a ring he planned to purchase for his wife.

"It was a large purple stone," LaBlue testified.

McGuire, 34, is charged with first-degree murder for the 2004 shooting death of her husband.

Her lawyers called a forensic computer expert Wednesday to dispute the significance of suspicious Internet searches presented to jurors in the prosecution's case. Those searches included research on guns, poison and murder.

The defense contends the victim conducted those searches. Their expert, Jesse Lindmar, said other Internet activity during that time was consistent with William McGuire checking his work e-mail, a process requiring a password.

He pointed to an April 11, 2004, search for "undetectable poison" that was done within two minutes of someone checking William McGuire's email.

"It's a minute and 59 seconds later," defense attorney Stephen Turano noted.

A search a week later for chloroform was followed five minutes later by a transfer of funds in a retirement account and a visit to William McGuire's e-mail inbox. On April 26, 2004, two days before the victim was last seen alive, e-mail use also occurred within 45 minutes of a search for "insulin shock."

State Superior Court Judge Frederick DeVesa asked Lindmar if it were possible that someone was accessing the couple's home computer from a remote location. He said that it was possible but that he had seen no evidence of it.

Under questioning by a prosecutor, Lindmar acknowledged that he could not say who had been sitting at the keyboard when the searches were done or if William McGuire had shared his e-mail password with his wife.

"You have no way of knowing whether someone else in the household jumped on the computer for a few minutes to let someone do a search and then returned to what they were doing," Assistant Attorney General Patricia Prezioso said.

The witness agreed.

Prezioso also quizzed him about a search for "morphine and poisoning" that was done within four minutes of a check of Melanie McGuire's work e-mail. Lindmar said he had not specifically looked for the instances where the searches coincided with use of the defendant's e-mail account.

The defense is expected to conclude its case Thursday. Jurors may begin deliberating Monday.