Nicole Beecroft's baby was born alive and struggled to breathe but died soon afterward from knife wounds, a Ramsey County medical examiner testified Thursday in Beecroft's first-degree premeditated murder trial.

"The stab wounds were inflicted while she was alive," Dr. Kelly Mills said of the baby girl whose body she autopsied in April 2007.

In extensive testimony in Washington County District Court, Mills described the nature of the baby's injuries and scientific documentation of what she said was proof of a live birth. Mills reviewed dozens of photographs that showed 135 stab wounds, most in the baby's upper body.

"It would be hard to pinpoint which injuries were the fatal wounds because there was so much internal damage," Mills said under questioning from prosecutor Siv Yurichuk.

Beecroft, now 24, has spent seven years in jail and prison on a life conviction without parole for killing her baby. Her new trial was ordered by the Minnesota Supreme Court last summer on grounds that two people not associated with the first trial had influenced testimony.

Beecroft was living in Oakdale with her mother when she gave birth to the baby and disposed of the girl's body in a trash can outside her house. The 17-year-old Tartan High School senior had disguised her pregnancy and was alone during the birth.

The fundamental question in the current trial is whether the 7-pound, 15-ounce girl was living or dead when Beecroft stabbed her repeatedly with a serrated kitchen knife. Her attorneys said their witnesses will prove the child was stillborn.

Mills testified Thursday that she took more than 200 photographs of Baby Beecroft, compared with a standard nine, because of all the injuries she found after unwrapping the body from a pink bath towel. In several instances the full-term baby was shown with thick brown hair, her head and face untouched, but with an array of red wounds across her chest, left arm, and neck.

X-rays showed air in the baby's lungs and stomach, Mills said, and "you don't see air in a baby that's stillborn or dead." She also said bruising confirmed a live birth because it's "how the body responds to injury."

Mills showed laboratory slides of the baby's lungs to support her conclusion that the manner of death was homicide.

"She was alive but didn't live long enough to expel all the amniotic fluid out of her lungs," Mills said. "They were aerated — indicative of live birth."

Defense attorney Christine Funk, in cross-examination, got Mills to acknowledge that she's read in medical literature that infants can inhale air and still die in the birth canal. Mills also told Funk that much of the air in the baby's body came from inflicted injuries.