Patients at California's board-and-care centers for the developmentally disabled have accused caretakers of molestation and rape 36 times during the past four years, but police assigned to protect them did not complete even the simplest tasks associated with investigating the alleged crimes, records and interviews show.

The Office of Protective Services, the police force at California's five developmental centers, failed to order a single hospital-supervised rape examination for any of these alleged victims between 2009 and 2012. At most other police departments, using a "rape kit" to collect evidence would be considered routine.

The procedure, performed by specially trained nurses, is widely regarded as the best way to find evidence of sexual abuse. Without physical evidence, it can be nearly impossible to solve sex crimes, especially those committed against people with cerebral palsy and profound intellectual disabilities.

In the three dozen cases of sexual abuse, documents obtained by California Watch reveal that patients suffered molestation, forced oral sex and vaginal lacerations. But for years, the state-run police force has moved so slowly and ineffectively that predators have stayed a step ahead of law enforcement or abused new victims, records show.

Nearly a third of the 36 alleged sex abuse cases occurred at the Sonoma Developmental Center in Eldridge, where patients, employees and parents have reported 11 assaults over the past four years, internal incident records show.

In one case from August 2006, caregivers at the Sonoma center found dark blue bruises shaped like handprints covering the breasts of a patient named Jennifer. The patient accused a staff member of molestation, court records show. Jennifer's injuries appeared to be evidence of sexual abuse, indicating that someone had violently grabbed her.

The Office of Protective Services opened an investigation. But detectives took no action because the case relied heavily on the word of a woman with severe intellectual disabilities. A few months later, court records show, officials at the center had indisputable evidence that a crime had occurred.

Jennifer was pregnant.

By that time, her alleged attacker had vanished.

For the parents of the 32-year-old patient, the reaction has been disbelief and anger. They are now raising a 5-year-old boy who Jennifer is incapable of mothering. The child is precocious and strongly resembles his maternal grandmother.

"Every time, I just imagine her being raped and screaming and crying for me," said the woman's mother, whose name is being withheld to protect Jennifer's identity. "It just kills me."

The Office of Protective Services has not collected physical evidence to back up cases such as Jennifer's. In situations involving developmentally disabled patients, DNA and other physical evidence are even more important because statements from alleged victims often are treated as unreliable. Some have IQs in the single digits and cannot speak.

Detectives at city and county police departments are trained to send sexual assault victims to an outside hospital for the specialized rape examination. But the doctors and nurses at the state's developmental centers -- in Sonoma, Los Angeles, Orange, Riverside and Tulare counties -- were not trained in dealing with sexual assault victims, records and interviews show.

California Watch shared details of the developmental center sex abuse cases with two outside police detectives who specialize in such assault investigations. The detectives said they were dismayed by the state's actions.

"How can you do a sexual assault investigation and not do an exam?" said Roberta Hopewell, a detective at the Riverside Police Department and president of the California Sexual Assault Investigators Association.

In another case at the Sonoma Developmental Center, which houses about 500 men and women, a caregiver was cleared by the center's internal police department of assault. Months later, he was accused of molesting a second patient.

The Office of Protective Services was first alerted in February 2009, when a female patient accused a caregiver of forcing her to perform oral sex on him.

"Client reported to staff that she saw (the caregiver's) genitals and was asked to perform oral sex for a dollar," the records said. "Client reports that she did."

However, the Office of Protective Services quickly closed the case, the records indicate, because the suspect was not listed as having worked in the patient's unit, called Corcoran, on the day of the alleged abuse. The accused caregiver did often work in that unit, though, internal records show.

Months later, the mother of a second patient said her daughter reported she had also performed oral sex on the same psychiatric technician. But by then, the accused caregiver was gone. He is not identified by his full name in state records.

According to interviews with former detectives and patrol officers at three of the state's developmental centers, the Office of Protective Services did not assign its own detectives to cases that should have been investigated -- nor did the force seek expert help from outside law enforcement.

One former patrol officer said administrators were afraid of bad publicity.

"They didn't want anything to get out, so they handled it internally. They call the shots," said Joe Guardado, a former patrol officer at the Porterville Developmental Center in Tulare County who retired in 2010.

The state Department of Developmental Services, which operates the five centers and oversees the Office of Protective Services, issued a written statement saying the state is working to protect patients and ensure they receive justice. That includes hiring "nationally recognized law enforcement experts" to train police officers and detectives to better handle sex assault cases, the department said.

"In addition, training was provided to ensure that referrals for sexual assault examinations are completed by thoroughly trained personnel, and that investigations are conducted appropriately and timely," the department said.

This story was produced by California Watch, a part of the independent, nonprofit Center for Investigative Reporting.