BAGHDAD, Iraq — Sunnis in Iraq are studying Shiite religious history and customs to enable them to bluff their way through illegal checkpoints set up by Shiite death squads.

Relatives and neighbors meet to share knowledge on the 12 imams revered by Shiites Muslims, test each other on the dates of Shiite festivals, or advise on where best to buy fake IDs with Shiite names, in case they are challenged at gunpoint. Web sites have also been established to help Sunnis learn how to pass themselves off as Shiites.

Such knowledge can be a matter of life and death as Shiite militias stop cars in the capital and demand to know if the driver is Sunni or Shiite.

The sectarian violence that followed the destruction in February of the Golden Mosque at Samarra, a revered Shiite shrine, shows no sign of abating.

Any driver identified as Sunni risks being kidnapped and tortured.

Their bodies usually found dumped in the River Tigris or on a garbage dump. Since Saturday, at least 74 bodies have been found around the capital — often, some Sunnis say, killed with the complicity of the predominantly Shiite police force in the city.

Last week, an entire Iraqi police brigade of 800 men was demobilized and sent for retraining after it was found to be helping Shiite death squads in northwest Baghdad.

It was fear of such a fate that led Omar, a van driver who takes food produce to markets around the city, to decide last month only to travel if he had two ID cards on him. Omar is one of the most recognizable of Sunni names, so for $25, he paid a friend with contacts in the printing industry to have another printed for him with his name as Haider, a typical Shiite name.

He also carries in his car a round piece of clay, which Shiite Muslims place on their foreheads when they pray.

A green cloth, the traditional symbol of the Shiite, is kept in the glove compartment for him to place over his car’s gear stick when he enters Shiite neighborhoods. “I am fortunate because my cousin’s wife is Shiite, so she helps me and my family learn how to act like a Shiite,” he said.

“I make all of us learn what she says. My children can now name all the imams and the year they were born and died.

“My oldest son even has a Shiite religious ringtone on his mobile phone he switches to when he has to go to Shiite areas.”

The doctrinal differences between Shiite and Sunni date back to the death of the Prophet Muhammad and a dispute about who should lead the Islamic community. Sunnis believe that it should have been Mohammed’s companions, while Shiite say that it should have stayed within his bloodline, through his son-in-law Ali and grandson Hussein.

Just two years ago, the suggestion that relations between the two sects in the country could ever reach such a nadir was ridiculed by Iraqis, who would describe how for generations Shiite and Sunni Muslims had intermarried, lived on the same streets, and worked beside each other.