Yet another investigation has uncovered concerns about a retired Vancouver psychologist's work in child custody battles, including allegations he used "nonsensical" assumptions to dismiss a mother's fears of violence by her ex.

The latest probe into Allan Posthuma wrapped up last month, when the College of Psychologists of B.C.'s inquiry committee issued a report alleging once again he had violated multiple sections of its code of conduct.

A Seattle psychologist hired by the college to review Posthuma's work in a high-conflict custody dispute concluded he "over-reached his test data" by dismissing the mother's fears that her life was in danger from her son's father, according to the complaint investigation report.

Dr. Marsha Hedrick wrote that Posthuma used a computerized personality test to rule out stalking or abuse by the woman's ex, a conclusion that "is nonsensical and gives the appearance of bias."

The new report comes on the heels of another five investigations that uncovered numerous ways Posthuma's work allegedly fell short.

As CBC News has reported, those investigations all ended when Posthuma retired at the end of 2018 after a four-decade career that saw him appear as an expert in hundreds of family law matters.

Because he gave up his registration, the college opted to cancel a planned disciplinary hearing, and there was never any conclusive finding of wrongdoing.

After this latest investigation uncovered fresh allegations, the college has again opted to not to take further action against Posthuma. The new report says "the public interest would not be served by maintaining further proceedings."

The mother whose complaint prompted the investigation says she's not satisfied with that response.

"There's so much damage that's been done. I can only imagine the other people that are affected by his files, because my family's been ripped apart," she said.

CBC News is not naming the mother in order to protect the privacy of her child.

The latest report highlights concerns about how Posthuma dealt with accusations of domestic violence during the mother's child-custody dispute, and how he interpreted the results of psychological questionnaires.

Posthuma recommended the boy's father as the more suitable parent, despite a history of violence and problems with aggression. A judge agreed with Posthuma, limiting the mother's parenting time to twice a month for two hours, under supervision.

The mother's lawyer, Carrie Humchitt, told CBC the father once beat the mother so severely that she miscarried a pregnancy.

"It was a documented pattern of violence, which wasn't really taken into consideration," Humchitt said.

The boy at the centre of the latest investigation told a psychiatrist, who was hired to review Posthuma's work, that his father was 'mean' and 'causes me to have bruises.' (Shutterstock)

The mother told CBC she felt "devastation" when she read Posthuma's assessment.

"[I thought], how do I protect my son, because his father's behaviours were very disturbing when we were together," she said.

The father has a criminal history that includes an assault charge, dealt with by peace bond in 2012.

A psychiatrist who assessed the couple's then six-year-old son in 2015 said the boy told him that "dad is really mean to me" and "he hurts me and causes me to have bruises," according to a letter written by the psychiatrist.

The letter says the father had a restraining order against him at the time because of an assault on his son, and that the boy had witnessed his father physically abusing his mother.

Questionable use of test results

According to the college's report, Posthuma dismissed the mother's allegations of abuse based on her results on a personality test called the MMPI-2-RF. The test consists entirely of true or false questions and is mainly used to assess mental disorders.

Making any conclusions about abuse "goes far beyond" what the test is intended for, according to Hedrick, the Seattle psychologist who reviewed Posthuma's work.

Hedrick also questioned why Posthuma used the results from something called the Wisconsin Card Sorting Test to conclude that the father had more potential "to learn more effective parenting skills."

That test is meant to assess cognitive reasoning and, according to Hedrick, there's zero research suggesting it can be used to say anything about someone's parenting.

Though Posthuma defended his work in conversations with the college, the report says the college inquiry committee shared Hedrick's concerns.

Parents who've filed complaints against Posthuma say much of their time with them was spent taking tests on a computer. (Ben Nelms/CBC)

The allegations echo those in previous investigations, which have repeatedly questioned Posthuma's interpretation of test data.

Parents who've spoken to CBC about their experiences with Posthuma all said they were surprised by how much of their time was spent answering multiple choice questions on a computer.

The mother who filed the most recent complaint said the testing made her anxious.

"I was home-schooled," she said. "I'd never done any formal testing before, so I was very scared going into it."

College registrar Andrea Kowaz told CBC she couldn't comment on a specific investigation. She has previously said that the public is often best served when a professional voluntarily cancels his or her registration, rather than going through a lengthy and uncertain disciplinary process.

Posthuma and his lawyer did not respond to requests for comment. He has previously told CBC that he is satisfied with his record and looks forward to spending more time with his family during retirement.