When Treshon Cousin hanged herself with a telephone cord in a St. Tammany Parish Jail holding cell last year, her family said they wanted answers about her death. Now, they are seeking their day in court.

Attorneys for her father, Michael Cousin, and her two young children — Alanna Cousin and Julius McFarland Jr. — filed suit Monday in federal court, alleging that Treshon Cousin’s constitutional rights were violated by the jail and the St. Tammany Parish Sheriff’s Office.

Besides those agencies, the lawsuit names Sheriff Jack Strain and several employees as individual defendants, alleging negligence that resulted in physical injuries. The lawsuit also names AmTel Inc., the company providing phone service for the jail.

The Sheriff’s Office had not yet been served Tuesday, according to Chief Deputy Brian Trainor, who said the agency does not comment on pending litigation. However, he issued a prepared statement about Cousin. “Suicide is a problem that affects too many families in our parish,’’ he said. “It is heartbreaking that this young girl chose to end her own life, just as so many young people do in St. Tammany Parish every year.’’

The suit claims that Cousin was not properly screened regarding her mental state and use of drugs or alcohol and that the jail’s phone system effectively denied her the right to call friends or an attorney. The suit also says the metal phone cord she used to hang herself was 30 inches long from the connection point to the handset, which it said is longer than prescribed by correctional standards, and that another female detainee had committed suicide in the same way in 2007.

“Therefore, as early as 2007, defendants possessed specific knowledge that a long telephone cord could be used as a hanging device by an arrestee/detainee/prisoner, and did nothing,’’ the suit says.

Cousin, who was 22, was brought to the jail on June 28 for $240 in unpaid court costs stemming from an arrest made when she had gotten into a fight while still in high school. She was awaiting booking on misdemeanor contempt-of-court charges when she hanged herself less than two hours after her arrival.

Initially, Cousin was in a holding cell with six other women, but they were moved, and she was left alone for about 45 minutes without anyone checking on her, the suit says.

Cousin, who had made 17 unsuccessful attempts to contact someone using the phone in the cell, made a final call 23 minutes after the other women were moved. She then wrapped the cord around her neck, dropping to her knees. She was discovered by deputies 20 minutes later. Although officers and medical staff who performed CPR restored her heartbeat, she died later in the hospital after her family removed her from life support.

Cousin’s frustrated attempts to contact someone by phone are a central part of the lawsuit, which notes that AmTel had a shared-revenue agreement with the jail that gave the company an exclusive license to install and operate pay-for-call equipment at the jail, with the Sheriff’s Office receiving a commission of 68.5 percent on all completed calls.

Prisoners and detainees are provided a free two-minute call, the suit says, but that can happen “if, and only if, the intended recipient can navigate the complex automated system.’’ The suit claims the system is so hard to use that it effectively denied Cousin her right to contact friends or legal counsel.

If a call goes through, the recipient is not told it is a free call. Instead, the suit claims, the recipient is led to believe he or she has to set up an account with AmTel and authorize a $15 charge to a credit card. Neither the Sheriff’s Office nor the phone company receives any revenue from the free calls, the suit says.

After several failed attempts, Cousin started saying “two free minutes’’ instead of her name when prompted by the system, the suit says. “However, Michael Cousin and the other individuals Treshon reached out to help that evening were totally perplexed by the burdensome and misleading telephone system.’’

Cousin’s mental state and the jail’s history of shortcomings in dealing with mentally ill prisoners — as outlined in a 2012 Department of Justice report — are another focus of the lawsuit.

Cousin was not asked proper questions during initial intake about her mental state or whether she had used drugs or alcohol, the suit claims, although a urine sample she gave tested positive for marijuana and methamphetamine.

The positive drug test should have triggered a health screening by medical personnel and closer observation of Cousin as a “special needs offender,’’ the suit claims.

The 2012 report by the Department of Justice’s Civil Rights Division “specifically criticized the jail for failing to properly train its employees to screen for mental health issues,’’ the suit says.

The Sheriff’s Office signed a memorandum of agreement with the federal agency in July of last year aimed at improving conditions at the jail. Among other things, the agreement requires an independent auditor to review compliance with the agreement and says the Sheriff’s Office must report any prisoner death or serious suicide attempt to the Justice Department and the independent auditor within 24 hours.

There have been no additional suicides or attempts at the jail since Cousin’s death, spokesman George Bonnett said.

Cousin’s father and stepmother told The New Orleans Advocate at the time of Treshon’s death that she was not suicidal and didn’t suffer from mental health problems.

The Sheriff’s Office also released a statement at the time saying that she revealed no history of mental illness or suicidal intentions. “There were absolutely no factors present to indicate she should have been placed under close observation or suicide watch,’’ the Sheriff’s Office said.

Follow Sara Pagones on Twitter at @spagones advocat.