The prosecution rested Wednesday in the court-martial of an Army dog handler accused of abusing detainees at Iraq's Abu Ghraib prison, after witnesses described treatment of prisoners that differed markedly by day and night.

Sgt. Santos Cardona, 32, of Fullerton, Calif., is accused of making his tan Belgian shepherd bite one detainee and harass another for his own amusement and that of other nightshift workers, characterized by prosecutors as a small band of "corrupt cops."

Staff Sgt. Christopher Ward, who supervised guards during the day, described an orderly environment sharply at odds with the widely seen photographs taken during nighttime hours of naked detainees being piled into pyramids, barked at by dogs and subjected to other humiliating treatment.

Ward said Wednesday that he had seen dogs used during the day shift in the prison about a half dozen times during his six months at Abu Ghraib, and only to patrol the tiers or search for smuggled weapons.

In contrast, Ward's night-side counterpart, former Staff Sgt. Ivan L. Frederick II, testified Tuesday that Cardona and another Army dog handler were inside the prison with their canines three to five times a week. Frederick described incidents in which the dogs were used at the request of interrogators to bark at detainees.

He also said he had heard Cardona say he was having a contest with another dog handler, former Sgt. Michael Smith, to see how many detainees they could make urinate on themselves.

Cardona is charged with assault, dereliction of duty, maltreatment of detainees, conspiracy to maltreat detainees and lying to investigators. He faces up to 16 1/2 years in prison if convicted of all nine counts.

The defense, which would begin presenting its case later Wednesday, was expected to include testimony from Maj. Gen. Geoffrey Miller, the highest-ranking officer called yet in the courts-martial stemming from the scandal.

Defense attorney Harvey J. Volzer has previously said he plans to call Miller, a former commander of the detention center at Guantanamo Bay who was later sent to Iraq, to testify about interrogation techniques.

A military investigation into FBI reports of prisoner abuse at Guantanamo recommended that Miller be reprimanded for failing to oversee the interrogation of a high-value detainee, which was found to have been abusive. But a top general rejected the recommendation. Miller, who took over detainee operations in Iraq in March 2004, recently requested early retirement.

Frederick, now a private, is serving an eight-year sentence for his role in the Abu Ghraib scandal. Smith, of Fort Lauderdale, Fla., was convicted at a court-martial in March of maltreatment, conspiracy, dereliction and an indecent act. He was sentenced to 179 days in prison.

Ten low-ranking soldiers have been convicted of abusing prisoners at Abu Ghraib, in many cases by forcing them to assume painful or sexually humiliating positions.