James Armstrong, accused of fatally shooting his cousin Ralph Sebastian Sidberry in the driveway of the victim's North Stonington home on April 12, will undergo an evaluation to determine if he is competent to stand trial for murder.

Armstrong, 30, who was extradited from Missouri last month, made his first appearance Tuesday in the New London Superior Court section where major crimes are tried. Armstrong and Sebastian Sidberry were cousins and members of the Eastern Pequot Tribal Nation.

Sebastian Sidberry, 31, also known as "Seqoyah, Tall Tree," died from a single gunshot wound to the back of the head, according to the state Office of the Chief Medical Examiner.

Judge Hillary B. Strackbein appointed the judicial district's chief public defender, Kevin C. Barrs, to represent Armstrong and said Supervisory Assistant State's Attorney Lawrence J. Tytla would be prosecuting the case. Barrs asked the judge to order a competency evaluation for Armstrong. The judge ordered the evaluation and continued the case to Oct. 30. Clinicians from the state will meet with Armstrong to determine if he is able to understand the court proceedings and assist in his own defense.

Armstrong, who is being held in lieu of $1.5 million at the Garner Correctional Institution — where inmates with mental health issues are confined — insisted on addressing the judge during the court appearance even after she told him he should speak to his attorney first. Armstrong said the victim had been spreading HIV among fellow tribal members. Blood tests taken during Sebastian Sidberry's autopsy showed he did not have the virus.

"Anyone could have done it, as Ralph Sebastian was spreading HIV to the Indians of Connecticut," Armstrong said. He alleged Sebastian had infected "at least five people."

During the investigation, family members told state police detectives from the Eastern District Major Crime Squad that Armstrong had no real friends, was unemployed and has been declining mentally over the last few years.

After the shooting but prior to his arrest, Armstrong's mother, Patricia Sebastian, a physician, had prepared an emergency committal letter for Armstrong, stating he was gravely mentally disabled and needed immediate care, according to an arrest warrant affidavit. Armstrong underwent a psychological evaluation at The William W. Backus Hospital on April 25 and was released, according to the affidavit.

"The letter stated among other things that James Armstrong has demonstrated a perseverance of untrue ideas and thought processes with disassociation between actual events and people," according to the affidavit. "James continues to make outlandish claims of widespread illness, specifically HIV/AIDS infection conspiracies through the use of syringes."

According to the affidavit, Sebastian Sidberry was out in his yard at 628 Lantern Hill Road building a stone walkway when Armstrong stopped at his house. Sebastian Sidberry's wife, Rebecca, who was pregnant with their second child, heard a gunshot from inside the home and went outside to find him lying on the ground.

Detectives identified Armstrong as a suspect and questioned him at his New London home within hours. He denied the shooting and told the detectives he had visited with Sebastian Sidberry in the yard for about a half-hour and left when Sebastian Sidberry said he was leaving soon. He admitted he had a .40 caliber pistol and submitted to a gunshot residue test. The test indicated Armstrong had lead, one of the elements of gunshot residue, on his left palm and the back of his right hand, according to the affidavit.

The detectives seized from a safe in Armstrong's bedroom a .40-caliber Kahr pistol and paperwork indicating Armstrong purchased it in January from the Newington Gun Exchange along with a box containing 50 rounds of ammunition. The pistol's magazine, which has the capacity to hold six rounds, only contained five rounds of ammunition, and detectives said they seized a total of 49 rounds in the safe.

Forensic testing indicated the pistol could not be eliminated as the possible weapon that fired a bullet recovered at the crime scene, according to the affidavit.

k.florin@theday.com