PHILADELPHIA -

The murder trial of a Philadelphia abortion provider has spawned courtroom debate over when life ends, as opposed to when it begins.

Dr. Kermit Gosnell is charged with killing four babies after they were born alive. Prosecutors said he cut the babies' spines after they were delivered and wouldn't have done so if they were dead.

In closing arguments Monday, Gosnell's defense lawyer called it "ridiculous" to say babies were still alive after in-utero injections of the heart-stopping drug Digoxen.

Gosnell's former staff members, however, have quoted the doctor as saying it was tough to hit the fetal heart through the abdomen, and they have testified they saw babies move, breathe or cry.

Jury deliberations are expected to start Tuesday.

Gosnell, 72, is also charged in the overdose death of a patient, 41-year-old refugee Karnamaya Mongar, of Woodbridge, Va.

Gosnell did not testify during his trial, but he could take the stand in the penalty phase if he is convicted of first degree murder. Prosecutors are seeking the death penalty.