Brittany Norwood, a former yoga store saleswoman convicted in one of Montgomery County’s most notorious and violent murders, should receive a new trial because prosecutors relied on police interviews in which she wasn’t told of her right to remain silent and to consult an attorney, according to an appeal of Norwood’s 2011 conviction filed Monday.

Prosecutors also improperly presented a police officer’s testimony as an expert opinion about a specific knife wound, Norwood’s attorneys argued.

Both of the legal matters were important in the trial, according to Norwood’s attorneys, because prosecutors highlighted the knife wound and the interviews in their closing arguments.

Norwood was convicted of killing co-worker Jayna Murray the night of March 11, 2011, inside the Lululemon Athletica store in downtown Bethesda. Norwood used at least six weapons in the attack and inflicted more than 331 wounds.

Norwood then cut herself, tied herself up, waited to be discovered the next day and told detectives that two men in ski masks had slipped into the store and attacked both women.

Brittany Norwood (Courtesy of Montgomery County Police)

A jury convicted Norwood of first-degree murder after deliberating for only 21 minutes. She is serving a life sentence without the chance of parole.

The filing Monday was Norwood’s first step in her appeal to the Maryland Court of Special Appeals. A response from the Maryland attorney general’s office is due Aug. 4, and the matter could be heard before the court as soon as the first week of September.

John McCarthy, the top Montgomery prosecutor who tried the case, said Monday that he and his staff stand by how they presented the case.

The knife wound to Norwood’s hand — one described by a police officer as similar to wounds he had seen by people wielding knives that slip in their hands — was not a big part of the case, McCarthy said.

“Within the volumes of evidence that spoke to her guilt, that was meaningless,” McCarthy said Monday.

The issue of the Norwood interviews came as detectives were trying to prove that Norwood had conducted the audacious coverup. On March 16, 2011, detectives asked Norwood to come to police headquarters to go over the story again, hoping to trap her in lies.

In seeking an appeal, Norwood’s attorneys argued that the detectives placed her in a room that at times was locked and that she felt she couldn’t leave. That should have triggered police to issue a Miranda warning, the lawyers wrote.

“Ms. Norwood felt that she needed the detective’s permission to terminate the encounter, as evidenced by her continued presence and participation in the interviews despite her clearly and repeatedly expressed desire to leave,” wrote Assistant Public Defender Juan P. Reyes.

Previously, Norwood’s trial attorneys had made a similar argument, but Montgomery Circuit Court Judge Robert Greenberg had ruled against them.

McCarthy said Norwood came and left on her own, accompanied by family members. The next day, Norwood arranged to come to police headquarters.

“She knew she’d been caught in a lie, and she wanted to spin the story again,” McCarthy said, adding that Norwood had orchestrated that interview.

But Norwood’s appellate attorneys wrote that she was quickly placed in a small room, given the impression she wasn’t free to leave and should have been issued her Miranda warning, according to Monday’s filing.

Get updates on your area delivered via e-mail