James Armstrong, charged with murder in the shooting death of his cousin in North Stonington in 2017 but never prosecuted because of mental illness, has successfully rebuffed attempts by state prosecutors to challenge his competency to stand trial.

New London County Assistant State’s Attorney Theresa Ferryman, who requested an independent competency evaluation of Armstrong in March, said Thursday that without Armstrong’s cooperation and without a new competency report, a previous ruling that determined Armstrong was not competent to stand trial is unlikely to change.

Armstrong, 36, is charged with murder in the April 12, 2017, shooting death of his cousin, 31-year-old Ralph Sebastian Sidberry outside Sidberry’s home in North Stonington on the Eastern Pequot Tribal Nation reservation. Sidberry’s daughter and pregnant wife were home at the time of the killing.

State police said Armstrong shot Sidberry because of a mistaken belief, or delusion, that Sidberry was spreading HIV to fellow tribal members. Medical tests showed Sidberry did not have the HIV virus.

Prior to being prosecuted, psychiatrists determined Armstrong had serious enough mental health issues that he was civilly committed. Past reports indicate Armstrong suffers from schizophrenia and personality disorder. Armstrong remains at Whiting Forensic Hospital in Middletown under the care of the state Department of Mental Health and Addiction Services.

As the result of the civil commitment, Armstrong is out of reach of the criminal courts with the exception of court-ordered competency evaluations every 18 months. There is no bond in the pending murder case. Ferryman said the most recent evaluation was completed on Nov. 9, 2022.

Armstrong’s case is overseen by the Probate Court system. New London Superior Court Judge John Newson said Thursday that he has no legal authority to order Armstrong to comply with the in-person interview needed to complete a competency evaluation.

Ferryman said Dr. Catherine F. Lewis, a professor emeritus of psychiatry at the University of Connecticut who was hired by the state for a second opinion on Armstrong’s competency, has been unable to complete a report. Without a new report, Ferryman said the court would have to fall back on the findings of the previous evaluation.

Newson said without a new report, there was no evidence to challenge the previous finding.

“There can’t be a credible hearing, and the state can’t challenge the competence finding without Mr. Armstrong’s participation,” Newson said.

An update on the competency evaluation is expected on March 18.

Katherine Sebastian Dring, Sidberry’s mother, has followed the case closely and was sitting in court on Thursday during the discussion. Sebastian Dring has consistently argued that it is an injustice not to prosecute Armstrong and has said she fears that he will eventually be released back into the community. She requested but was not allowed to address the court.

g.smith@theday.com