An autopsy found morphine in the boy's body, police said, but the cause of death is undetermined, a spokesman for the Philadelphia Medical Examiner's Office said.
According to the police account in the affidavit of probable cause, police responded to a call of an unresponsive baby at the Neshaminy Inn Motel on Route 1 on July 3, and found the boy on a makeshift bed on the floor. They performed CPR, but the boy, identified as T.K., was pronounced dead.
The officers found syringes, empty heroin bags, and a spoon used to cook heroin within reach of the boy and the couple's two other young children.
The family had been living in motel rooms along Route 1 for about a month. Krolikowski said he didn't know what had happened to the baby "because he was in and out of the motel room throughout the night waiting for his drug dealer to arrive with more heroin."
Both parents submitted to blood tests, which found morphine in their systems. Heroin metabolizes into morphine, the county crime lab toxicologist reported.
The couple were not arraigned until Thursday because police were waiting for the medical examiner's report and to determine the proper charges, a department spokesman said.
Contact Bill Reed at 215-801-2964, firstname.lastname@example.org, and @breedbucks on Twitter. Read his blog, BucksInq, at www.philly.com/bucksinq.