There are more than 50 cases where coroners in the U.S. have listed a stun gun as a factor in a death, according to new research from Amnesty International.

Three of the X26 Tasers tested by U.S.-based lab National Technical Systems as part of a CBC/Radio-Canada investigation into the devices. (CBC)

The findings, contained in a report released Tuesday on Taser use in the United States, have prompted the human rights organization to reiterate its call for a moratorium on the stun gun's use until more medical and scientific studies have been done.

The report includes an independent analysis of 98 autopsy reports on people who died in the U.S. after being hit with a Taser.

The analysis by a Norwegian professor of forensic pathology found many of those who died had received multiple or prolonged shocks and went into cardio-respiratory arrest shortly after. Some died at the scene while others were pronounced dead at a hospital.

The Amnesty report noted that while most of those who died were agitated, disturbed or on drugs, 90 per cent were unarmed.

"Tasers are not the 'non-lethal' weapons they are portrayed to be," the report's author, Angela Wright, said in a statement.

"They can kill and should only be used as a last resort."

Amnesty said many police departments allow stun guns to be used in situations where the level of threat is well below one where officers would be authorized to use lethal force. The organization said some even classify Taser use at the level of "hands-on" force or just above "verbal demands."

If governments and the police are not prepared to put a stop to Taser use, the report says, Tasers should at least be put in the same category as a firearm — a weapon with the potential to kill.

The head of Amnesty International Canada, Alex Neve, said it is time for police to either stop using the Taser or severely restrict its use.

"They need to immediately adopt polices that make it very clear that a Taser will only be used if the only other choice open to a police officer is to use his or her firearm."

Neve said putting the stun gun in the same class as a firearm should not just be a police policy, but should be backed up in law.

"Governments should step in here and make it a criminal offense to use Tasers in other circumstances, to make it very clear that this is serious," he said.

Police forces across North America have sought to assure people that Tasers are safe. One of the leading manufacturers of stun guns, Taser International, has said its product has a higher safety margin than Tylenol.

Tasers are supposed to allow police officers to subdue violent individuals without killing them or worrying that a stray bullet might kill or injure an innocent bystander.

Law enforcement officials have argued that not enough attention is paid to the number of lives stun guns have saved by allowing officers to respond to situations without using traditional, more forceful tactics.

Earlier this month, Amnesty International renewed its call for a moratorium on Taser use after tests commissioned by CBC News and Radio-Canada found some of the stun guns deliver a stronger electric shock than the manufacturer claims.

Of the 41 Tasers tested, four delivered significantly more current than Taser International says is possible. In those cases, the current was up to 50 per cent stronger than specified for the devices.

The X26 model Tasers evaluated were made before 2005, prompting some scientists to suggest police should stop using any older versions of the stun guns until they can be tested.

The RCMP has since said it's pulling X26 units acquired before the beginning of 2006 from the force for testing.