When the twin girls arrived at St. Christopher's Hospital for Children in March, just two months after they were born, both had broken legs.

One also had a fractured rib and an injury of the spine - indicative of shaking. Both were malnourished. Some injuries were new, others old.

Both girls, Bucks County authorities allege, were hurt at the hands of their mother and father.

In court documents filed Sunday, investigators described a pattern of abuse inflicted by a Tullytown couple on their infant daughters - at times so severe that investigators say the injuries could have resulted in death.

The charges against Michael Shales, 30, and his wife, Melissa, 25 - which include endangering the welfare of a child, conspiracy, and aggravated assault - capped a two-month investigation that began when Melissa Shales called 911 to report that one daughter was having trouble breathing. Both parents were arrested Sunday.

The affidavit of probable cause gives the following account:

On March 21, Melissa Shales contacted emergency services to report that one daughter had choked on a piece of cloth that day and was having trouble breathing. When police arrived, they found an apartment in "deplorable condition," with soiled diapers, dirty dishes, and rounds of rifle ammunition scattered on the floor.

Michael Shales allegedly told a neighbor that his daughter had choked on cotton, and that he stuck a pair of pliers down her throat in an attempt to remove it. After it was removed and the child continued to have trouble breathing, he said, 911 was called.

The child was taken to St. Mary Medical Center in Langhorne, but her injuries were so severe that she was transferred to the intensive care unit of St. Christopher's, according to the affidavit.

A doctor notified police of the numerous injuries to the girl - including lacerations on her mouth and genitals, and fractures of her leg - all of which the doctor declared "non-accidental." The fracture to her leg was so severe, the doctor advised police, that left untreated, the injury could result in deformities or death, the affidavit says.

The other twin and the couple's 2-year-old son subsequently were taken to the hospital for evaluation. There, doctors discovered injuries on the girl consistent with "pulling, shaking, or twisting," investigators alleged.

Melissa Shales "admitted to doing certain things out of anger to the children in front of Michael to get a reaction out of him," the affidavit says.

It is unclear whether the couple's son sustained any injuries.

The couple remained in the Bucks County prison Monday afternoon with bail set at $500,000 each. No attorney information was available. A preliminary hearing for both has been scheduled for next Tuesday.

cmccabe@philly.com

610-313-8113 @mccabe_caitlin