A reservist convicted of abusing detainees at the Abu Ghraib prison in Iraq testified yesterday that two Army dog handlers set their dogs on prisoners and laughed about a competition to scare prisoners into urinating on themselves.

The accusations against Sgt. Santos A. Cardona and Sgt. Michael J. Smith came on the first day of an Article 32 hearing at Fort Meade. The hearing is the military equivalent of a grand jury proceeding and was the first such Iraqi prisoner abuse hearing to be held in Maryland.

Government witnesses recounted scenes of naked detainees being threatened and bitten by snarling dogs. The defense sought to portray two of the soldiers as lying in the hope of getting their sentences reduced.

Neither Cardona nor Smith is from Maryland or was a member of the 372d Military Police Company of Cresaptown, which has been embroiled in the prisoner abuse scandal. Fort Meade was chosen for this week's hearing largely for its facilities.

In telephone testimony from Fort Leavenworth, Kan., where he is serving eight years for his role in the abuse, Pvt. Ivan L. "Chip" Frederick II described a chaotic scene that included Cardona, Smith and Pvt. Charles Graner Jr., already convicted in the Abu Ghraib scandal.

Frederick described an incident in which a frightened detainee was on the ground in his cell, with Cardona and Smith's dogs barking and growling. When the detainee slapped Graner, Cardona released his dog, which bit the detainee on the thigh. When the detainee tried to flee, he was bitten again, Frederick said. The wounds required stitches.

He said Smith's dog later bit another detainee on the wrist.

Frederick said the sergeants laughed about having a contest to frighten detainees. "They were having a conversation about who can get the most detainees to urinate on themselves using the dogs," he testified.

Cardona, 31, of Fullerton, Calif., is a sergeant with the 42nd Military Police Detachment at Fort Bragg, N.C. He is charged with prisoner cruelty, conspiracy to maltreat detainees, aggravated assault, dereliction of duty and lying.

Smith, 24, of Florida, is a sergeant with the 523rd Military Police Detachment at Fort Riley, Kan. He is accused of prisoner cruelty, aggravated assault, conspiracy to maltreat detainees, dereliction of duty, committing an indecent act and lying.

Both men are accused of conspiring with Graner, Frederick and civilian interrogator Steve Stefanowicz. Graner, like Frederick, was convicted of abuse, demoted and is serving a prison term. Stefanowicz has not been charged with a crime.

Some testimony implicated Col. Thomas M. Pappas, then head of the 205th Military Intelligence Brigade at Abu Ghraib, in the use of muzzled dogs to scare prisoners into cooperating. Pappas was reprimanded and fined in May.

Harvey Volzer, civilian attorney for Cardona, said outside the courtroom that he plans to argue that military higher-ups permitted mistreatment.

Among others who testified yesterday was Pvt. Sabrina Harman, a 372nd reservist convicted of conspiring with Graner. In telephone testimony from the Miramar Navy brig, she also described the dog-biting incident involving Graner, though she could not identify the dog handlers.

The hearing is expected to continue at least through today.