The Young and the Restless star's 24-year-old son, Julian, was on suicide watch at La Casa Mental Health Rehabilitation Center in Long Beach when he died, and St. John and his ex-wife Mia claim his death could have been prevented if staff had not been so negligent.

In documents obtained by TheWrap.com, St. John alleges care workers and counsellors failed to check in on his son every 15 minutes, leaving Julian, who suffered from schizophrenia, alone for nearly an hour without supervision.

Julian was found face down with a plastic bag over his head in November (14).

The actor also accuses staff members of falsifying documents of the 911 calls made to emergency responders, claiming the facility's timeline of the incident does not match up with those of the paramedics.

In an emotional interview with Entertainment Tonight, which aired in America on Tuesday (26May15), St. John said he and his ex-wife decided to take legal action against the care facility's bosses at sister company Telecare Corporation in the hope they can help make sure a similar incident doesn't happen to other patients in mental health centres.

He says, "This lawsuit is to shed light on the inefficiency and the incompetency that happens in mental hospitals nationwide... We have a bad health care system... People should never die in the hospital for lack of care... At the end of the day, his life will not be in vain."

Mia told the news show, "What we do know is that he attempted suicide two and a half weeks prior."

Her ex-husband added, "He tried to commit suicide with a plastic bag. That's contraband. They're all over the hospital, so we know that they never removed the plastic bags after the first time that he tried to commit suicide."

St. John is suing Telecare executives for negligence, negligent supervision, negligent retention and wrongful death, and he is seeking an unspecified amount in damages.