Some 12 years after the execution-style slayings of three people at Tantalus lookout and a subsequent home invasion robbery that terrorized three others, a Circuit Court judge ruled this week that suspect Adam Mau is unfit to stand trial due to brain damage and severe mental illness.

Judge Rom Trader dismissed with prejudice a pair of indictments against Mau and ordered him to be involuntarily committed to a mental institution.

“Where the court determines that the accused is not fit and unlikely to be restored to fitness in the foreseeable future, it is appropriate that the criminal prosecution end and the individual to be subject to civil commitment proceedings,” Trader wrote in a Findings of Fact, Conclusions of Law and Order document. “In these cases, the circumstances supporting the dismissal are rooted in the likelihood that Defendant suffers from untreatable cognitive deficiencies and physical injury to his brain that will substantially impair his ability to rationally understand the proceedings against him and to meaningfully assist in his own defense.”

The ruling, filed Tuesday, affirms Mau’s inability to participate in his own defense; it does not address his guilt in the alleged offenses or his mental state at the time of the incidents.

According to prosecutors, Mau took a taxi to Tantalus on July 6, 2006. There he allegedly shot the driver, Manh Nguyen, and Jason and Colleen Takamori, who had gone to the lookout to take pictures. All died of gunshot wounds to the head.

That same evening, prosecutors said, Mau broke into a Round Top Drive residence, bound and taped a couple and their housekeeper, and stole the couple’s car.

Mau was arrested soon after and charged with 18 felony counts, including first-degree murder, three counts each of second-degree murder and kidnapping, first-degree burglary, first-degree robbery, first-degree theft and multiple firearm offenses.

The charges were contained in one of the two indictments dismissed this week. The other indictment contained three charges related to a Sept. 15, 2016, incident in which Mau is alleged to have assaulted personnel at the Hawaii State Hospital, where he had been held pending a determination of fitness.

In rendering his decision, Trader noted the preponderance of evidence that Mau lacks the capacity to understand the proceedings, consult with his attorneys and assist in preparing his own defense.

Trader noted Mau’s “long and well-documented history of serious mental health concerns,” which possibly started at birth when he suffered a brain blood-oxygen deficiency and included at least six verified head traumas between the ages of 6 and 19.

In 2002 Mau was involuntarily hospitalized in the psychiatric ward of The Queen’s Medical Center after threatening his family. He was observed suffering auditory hallucinations and paranoid delusions that centered on his belief in a war that was to be waged by the “Nation of Hawaii.” He was later diagnosed as paranoid-schizophrenic by multiple evaluators.

Mau’s attorney Brook Hart said the inordinate amount of time that it took to rule on his client’s fitness — the longest he’s seen for such a determination in his 50-plus-year career — was largely due to the “very difficult, elaborate and intricate” details of Mau’s mental health profile and the mountains of documentation that tell the story, including 35 separate reports by 11 different mental health experts and more than 16,000 pages of observational notes from Mau’s stay at the Hawaii State Hospital.

Ultimately, Trader ruled that Mau had only a “basic level of understanding” about the proceedings against him despite 10 years of treatment and that it was inadequate for the demands of an active defense.

“Mr. Mau is unable to comprehend, or understand, a conversation in which he is asked a complex or abstract question,” Trader wrote. “He cannot remember the beginning of the question, or the scenario, when the speaker finishes.”