The mother of a 15-month-old Maryland boy who police say was drowned by his father is suing the psychologist who testified that the accused killer was capable of having unsupervised visits.

Hera McLeod, 32, of Gaithersburg, is seeking $20 million from Ashburn Psychological Services and one of its psychologists, Margaret Wong. The lawsuit was filed in Fairfax County Circuit Court on Tuesday morning.

On Oct. 20, Joaquin Shadow Rams fatally injured his son, Prince Elias McLeod Rams during the child's fourth unsupervised visit, according to court documents. McLeod said Tuesday that it was her understanding that Rams took off all of Prince's clothes and held him under water. The child died after being taken to a Fairfax hospital.

In January, Rams was charged with first-degree murder. Prior to the drowning, Rams took out life-insurance policies on Prince that totaled about $550,000, according to a police investigation.

McLeod said she separated from Rams two weeks after Prince's birth in July 2011. Rams petitioned to get unsupervised visits. As part of his efforts to have a judge grant him lenient visitation rights, Rams paid Ashburn Psychological Services to perform an evaluation, McLeod said.

Wong, who did the testing, then testified in Montgomery County Circuit Court that it was safe for Rams to visit his young son without supervision. As a result, a judge granted the visits.

During Wong's testimony, she disregarded evidence that Rams was unstable, McLeod said. The lawsuit said that the defendants were negligent because they failed to investigate the fact that Rams was a suspect in the 2003 death of his ex-girlfriend and failed to diagnose Rams with a personality disorder.

"[Rams] essentially paid them to ignore evidence and to lie for him," said McLeod, an intelligence analyst and former contestant on "The Amazing Race" reality show.

McLeod said that she decided to bring the lawsuit to hold accountable those who contributed to Prince's death.

"This issue's of utmost importance to me because my son is my heart," she said.

Wong and the director of Ashburn Psychological Services did not respond to requests for comment on Tuesday.