OKLAHOMA CITY (AP) – A woman who died after a policeman shocked her twice with an electronic stun gun had cocaine in her system and the drug contributed to her death, the state Medical Examiner’s office said Friday.

Milisha Thompson, 35, died May 19 after police stunned her with a Taser while she was on the ground and in handcuffs.

Thompson died of “excited delirium,” a situation in which a person’s heart becomes overtaxed from the effects of drugs combined with a high level of stress, Rob Deaton, an investigator with the medical examiner’s office said.

The death was ruled accidental, and the electrical stun gun was not listed as contributing to the death, he said.

Two officers had been investigating a report of drug activity when Thompson ran up to the officers. She was being disruptive, so they put her in handcuffs, police said.

Thompson continued to be combative, so officers used the Taser, stunning her twice in the neck, police chief Bill Citty has said. She soon stopped breathing.

“There is no reason to Taser somebody in handcuffs,” said Mike Gassaway, an attorney for Thompson’s estate.

Gassaway called the medical examiner office’s ruling a “fabricated cause of death” and questioned its accuracy. Police watchdog groups, such as the American Civil Liberties Union, have questioned whether “excited delirium” really is a medical condition.

Gassaway said Thompson’s family plans to have her body exhumed and have an independent autopsy performed.

“We’re not going to let them get away with this,” he said.

Citty has said officers acted appropriately because Thompson was kicking and posed a danger even though her hands were shackled.

Amnesty International USA has counted 250 cases in which people died after being stunned with a Taser. The human rights organization cannot say whether the shock from a Taser actually caused those deaths.

Tasers have been officially listed as a contributing factor in about 12 deaths nationwide, said Steve Tuttle, a spokesman for Scottsdale, Ariz.-based Taser International Inc., which makes the weapon. He said 11,000 U.S. law enforcement agencies use Tasers.

Some of those agencies have prohibited the use of Tasers on handcuffed suspects.

Deaton said he did not have information on how much cocaine was in Thompson’s system, and said a copy of her autopsy report would be available Monday.