Gosnell is in a Philadelphia prison without bail, charged with eight counts of murder in the deaths of a patient and seven newborns.
Tasha Jamerson, spokeswoman for Williams, says filing the notice does not necessarily mean that capital punishment will be sought if 70-year-old Gosnell is convicted.
Jamerson said prosecutors are required to give such notice at a formal arraignment or a death sentence cannot be sought.
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Also on Tuesday, a judge froze Gosnell's assets so that alleged victims may sue in civil court.
Gosnell is charged with killing seven babies born alive and with the death of a 41-year-old refugee after a botched abortion at the clinic, which prosecutors have called a drug mill by day and abortion mill by night.