PHOENIX (Reuters) - An Arizona nurse pleaded not guilty on Tuesday to raping a severely disabled woman in a crime that only came to light when the victim unexpectedly gave birth in the long-term care facility where she had been a patient for about two decades.

Nathan Sutherland, 36, wearing an orange jumpsuit and shackled at the wrists and legs, entered his plea during a brief arraignment at the Maricopa County Superior Court. His next court appearance was set for March 19.

Sutherland, a licensed practical nurse who began working at Hacienda HealthCare Skilled Nursing Facility in Phoenix in 2012, has been charged with one count each of sexual assault and abuse of a vulnerable adult. He has been held on $500,000 bail since last month.

Police said they arrested Sutherland on the basis of DNA evidence after the woman, who is in her 20s, went into labor on Dec. 29 at Hacienda HealthCare. Investigators collected DNA samples from all male employees of the facility.

Sutherland’s lawyer, Dave Gregan, said after the arraignment he would work to uphold his client’s due process rights.

“Mr Sutherland, just as you and I are, is entitled to a full defense,” Gregan told reporters.

Gregan has previously said prosecutors lack direct evidence of guilt, that the defense would conduct its own DNA tests and that Sutherland had no prior criminal history.

The woman was disabled by seizures during early childhood and has spent most of her life in the nursing facility.

Although she was initially described by authorities as comatose, her parents have said that she is capable of responding to sound and making facial gestures, and she has some ability to move her limbs, head and neck.

Hacienda has said its employees were unaware the woman was pregnant before she went into labor, according to police.

The governor of Arizona, Douglas Ducey, urged the state attorney general to open an investigation of Hacienda for its “actions and lack thereof in relation to the rape,” including the staff’s “failure to notice that the patient became pregnant prior to the birth of her child.”

Ducey, in a letter, also called for the attorney general to seek civil penalties against Hacienda and a reorganization “to ensure that nothing like this ever happens again.”

The facility has said Sutherland was dismissed as soon as administrators learned of his arrest, and that he had undergone extensive background checks before being hired.

The baby, a boy who is being cared for by family members, is doing well, police have said.

Arizona regulators have ordered Hacienda to contract with a third-party management company to assume day-to-day operations of the facility. But Ducey said the company has since said it cannot afford the cost of such outside management.