BOSTON -- Last week, Team 5 uncovered the case of Nelson Rodriguez, a mentally ill prisoner who took his own life while in Walpole State Prison.

NewsCenter 5's Janet Wu reported that Rodriguez was among many mentally ill inmates behind bars in Massachusetts, a fact that the Department of Correction acknowledged Monday.

According to the Romney administration, 19 percent of all men in the Massachusetts Corrections system suffer from mental illness and 66 percent of women do.

Advocates for inmates believe the numbers are higher.

Rodriguez, diagnosed as mentally retarded and severely mentally ill, was the last of four suicides in the state prison system last year. Team 5 learned from several sources familiar with his case that he threatened to kill himself just hours before he died. But on Monday, other families testified his situation was not unusual.

Frances Armstrong's nephew killed himself just two months earlier.

"I really believe that he was allowed to commit suicide. He was taunted by corrections officers. One of them actually, the night he committed suicide, asked him to please not to commit suicide before 10 o'clock because he didn't want to stay and do the paperwork," she said.

Corrections Commissioner Kathleen Dennehy testified before a joint committee Monday, but she appeared to know little of Armstrong's suicide. Dennehy said the investigation into Rodriguez's December suicide is still ongoing. But legal advocates for inmates said the problem is much larger than four suicides.

"The suicides are just the tip of the iceberg. The real problem is the self-mutilations and destructiveness of people who actually succeed, if you will, at the suicide," said Leslie Walker, of Massachusetts Correctional Legal Services.

Kristen Oliveras fears her brother is next.

"I'm scared that he could commit suicide one day. He has attempted it many times, he has been close many times," she said.

But the commissioner said many inmates' threats can't be taken seriously.

"It is not necessarily a reflection of (the system.) They fully know what they are doing and they are doing it to manipulate the system," she said.

But Rep. Ruth Balser, co-chairwoman of the joint committee on Mental Health and Substance Abuse, said the Romney administration's philosophy and culture of "lock 'em up and slam the door shut" is not working.

Balser's committee is pushing for legislation to set new standards for treatment and establish separate facilities for the severely mentally ill.