The little-girl voice on the police recording, lacking emotion, repeatedly assured an investigator that she was telling the truth about giving birth to a stillborn baby.

“No movement of the baby at all?” Oakdale police investigator Joseph Groppoli asked Nicole Marie Beecroft, then 17 and a senior at Tartan High School.

“No,” Beecroft replied in a casual tone of voice during the interview in April 2007.

“You’re sure?” Groppoli fired back, sounding increasingly skeptical of her answers.

“Positive,” she replied.

That central question of whether Baby Beecroft, as she’s known in court documents, was alive or dead when her teenage mother stabbed her 135 times will play out this week in a Washington County courtroom when several medical doctors debate the science of birth.

The trial is a fresh start for Beecroft, sentenced in 2008 to mandatory life in prison without parole on an indictment of first-degree premeditated murder. Last year, a divided Minnesota Supreme Court ordered a new trial for Beecroft, now 24, on grounds that interference from the Dakota County attorney and a medical examiner not connected with the case undermined her defense. At issue was whether other medical examiners they discouraged from testifying in her first trial could have shown that the baby was stillborn, thereby negating the murder indictment.

Prosecutor Siv Yurichuk opened the trial Monday with allegations that Beecroft had confirmed her pregnancy with a clinic but did not tell even her mother. The overweight girl succeeded in disguising the pregnancy until she delivered the full-term child in the laundry room of her mother’s house and later wrapped the body in a towel and tossed it into a trash bin outside.

“Why would anybody stab an already dead baby 135 times?” she said in her opening statement.

The emotional case won’t be presented to a jury because Beecroft requested a bench trial, meaning Chief Judge John Hoffman will decide a verdict at the end.

Defense attorney Christine Funk, told Hoffman that expert witnesses would testify that Beecroft’s baby was already dead before she inflicted wounds. That timing, she said, is the “essential question” before the court.

In a 50-minute police audio recording played in court, Beecroft described how she had given birth and said the baby was born dead. In that interview, responding to questions from investigator Groppoli, Beecroft didn’t reveal that she had stabbed the child.

“The truth is the most important thing we can get right now,” Groppoli told Bee­croft, who said again and again that she thought the baby was born dead.

“You’ve shown no emotion toward the child. I’m baffled. I don’t understand it, your mother doesn’t understand it,” he told Beecroft as her mother, Kari, sat beside her at the Oakdale Police Department. Kari Beecroft angrily told her daughter: “You don’t even realize what you’ve done.”

Finally, her voice breaking as the tape ended, Beecroft replied: “I did not kill it.”

Early the next morning, investigators found Baby Beecroft’s body in a blue trash bin outside the front door of her house. They also found a brown-handled steak knife in the garage.

Beecroft, wearing a black and white striped dress instead of jail clothes, sat with her head bowed while the recording was played in court.