NEW BRUNSWICK, N.J. — Jurors in the trial of a fertility nurse accused of killing her husband heard Tuesday about suspicious Internet research performed on the couple's home computer before the slaying, including one Google query for "how to commit murder."

The approximately 40 searches detailed by a forensic computer examiner called by the prosecution occurred on three occasions in the weeks leading up to William McGuire's disappearance. The topics searched related to poisons, guns and death. Among them were "instant undetectable poison," "toxic insulin levels," "how to commit suicide tips" and "how to purchase guns illegally," the expert said.

Prosecutors maintain Melanie McGuire, 34, used the Internet to plot her husband's 2004 slaying. A defense attorney told jurors in his opening statement last week that the 39-year-old victim, a computer analyst, was the primary user of the Hewlett-Packard and had conducted the searches in question.

Jennifer Seymour, a former analyst for the state police's digital technology unit, told jurors there was no way technologically to tell whether the defendant, the victim or someone else in their home had performed the searches.

But under questioning by a prosecutor, she noted that her examination of the same computer uncovered romantic e-mails between Melanie McGuire and her boss, a married physician.

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"The e-mail messages appeared to be some conversation between people who appeared to be having some intimate relationship," Seymour said. She was not asked to elaborate on the contents of the letters, but said it appeared that someone had tried to delete them.

Prosecutors allege McGuire used a sedative, chloral hydrate, to disable her husband of five yeas and then shot him three or four times before dismembering him with a power saw and throwing him in the Chesapeake Bay.

The searches conducted on the home computer included a query for chloral hydrate and its side effects. The day before McGuire is alleged to have killed her husband, someone filled a forged prescription for the sedative at a Walgreens pharmacy near the preschool attended by the couple's two children.

Seymour said the search for information about chloral hydrate occurred about a minute before a search on the Walgreens Web site for store locations.

The director of the McGuire children's preschool, Donna Todd, testified Tuesday that computerized records indicate Melanie McGuire dropped the boys off for class about 12 minutes before the prescription was filled at the pharmacy, a two-minute drive from the school.

The prescription was written on the pad of Dr. Brad Miller, the clinic doctor having an affair with McGuire, and made out in the name of Tiffany Bain, a clinic patient.

On Tuesday, Bain briefly took the stand and told jurors she was never prescribed the sedative and did not know how her name came to be on the prescription.

A lawyer for McGuire repeatedly tried to confront Seymour with data about other Internet activity performed at the same time as the suspicious searches. Stephen Turano previously told jurors that Internet use linked the victim, not the defendant, to the searches in question. State Superior Court Judge Frederick DeVesa, however, sustained prosecution objections to the questions, ruling that Seymour could not testify about data in reports she had not prepared.

The defense is expected to call its own computer expert later in the trial.

Testimony continues Wednesday. The trial is being streamed live on Court TV Extra.