Police detained a woman who was under an alcohol rehabilitation program at Phoenix Sky Harbor International Airport, but she died soon after the arrest.
"I can't confirm that she had alcoholism, but that certainly is my assumption," said Michael Manning, who was hired by Carol Anne Gotbaum's family over the weekend to monitor the police investigation.
He said it does not seem possible that Gotbaum could have strangled herself in custody.
Gotbaum, 45, became angry Friday when she was late for a flight and a gate crew did not let her on the plane. Officers handcuffed her behind her back and took her to the holding room, where she kept screaming, authorities said.
Police spokesman Sgt. Andy Hill said officers checked on Gotbaum regularly. During one check, officers found her unconscious with her hands "pressed against her neck area," Hill said.
"We don't know why or how she did it, but you have to assume that when someone is handcuffed behind their back that most probably she brought them from underneath herself and back up high."
"It doesn't make any sense," he said. "She was handcuffed behind her back and shackled to a table. It doesn't make sense that she could have physically managed to strangle herself."
Manning said he plans to send a representative to watch the county medical examiner's autopsy on Tuesday. He will conduct his own inquiry into whether police followed proper procedure.
"We are not jumping to any conclusions, but the circumstances surrounding Carol's death appear to be unusual enough to raise serious questions and warrant a thorough investigation," Gotbaum's stepmother-in-law, Betsy Gotbaum, said in a statement.
"Carol, who was only 5 foot 7 and 105 pounds (47 kilograms), appears to have been manhandled by the Phoenix Police Department. ... She cried out for help at the airport, but her pleas appear to have been met by mistreatment," the statement said.
Manning said the family has not decided whether it should file a lawsuit against Phoenix police.
"We're not going to jump to any conclusions without any evidence," he said.
Hill said officers followed established policy while detaining Gotbaum.