Updated

An autopsy shows that a knife, not an ax, killed a Michigan woman whose son's grandmother is charged with murder in the slaying.

Onita Higdon of the Detroit enclave of Highland Park pleaded not guilty Wednesday to first-degree murder charges in Monday's slaying.

Witnesses had said they saw 53-year-old Higdon with an ax Monday. But an autopsy showed 26-year-old Mila Perry of Detroit was killed by multiple knife wounds. Perry was the girlfriend of Higdon's son and mother of Higdon's 3-year-old grandson.

Police arrested Higdon after a standoff at her son's home. The grandson was in the house, but wasn't injured.

Higdon is jailed without bond and will get a court-appointed lawyer.