With California under an order from the United States Supreme Court to shed thousands of inmates from the state prisons, county jails are expected to receive many more inmates in the next year, which could aggravate overcrowding and other problems. Officials from the Sheriff’s Department have said that they will not place inmates from the state in the Men’s Central Jail, which they concede is an antiquated building.

But lawyers from the A.C.L.U. say that the Los Angeles County system is, in many ways, even worse than the state prisons that have been found unconstitutional. They say that many complaints are never properly investigated, and that often the very guards accused of abuse are in the room when an inmate is interviewed about the complaint.

In the last several months, the civil rights group has amassed 70 declarations from former prisoners and civilians who witnessed beatings. The statements suggest few patterns — the complaints span all times of day and multiple units in the jail. But, the A.C.L.U. says, the guards do seem to use the same terms repeatedly, shouting, “Stop resisting!” and “Stop fighting!” while they hit inmates, even when inmates are not moving or are in handcuffs.

Paulino Juarez, a Roman Catholic chaplain who has worked in the jail since 1998, was visiting an inmate’s cell early one morning in February 2009 when he heard several thumps and gasps in the hallway. When he moved to the cell door, he saw three deputies hitting a man and yelling, “Stop fighting!”

“But he wasn’t fighting; he wasn’t even defending himself,” Mr. Juarez said in an interview. “When they saw me, they froze. I was frozen, too. I didn’t say anything. I was too shocked, and I was terrified.”

Mr. Juarez filed a report with the Sheriff’s Department but did not hear anything about it for several months. More than two years later, during a meeting with his supervisor and Sheriff Baca, Mr. Juarez was told that the department found that the inmate had resisted going into his cell. There was no record of Mr. Juarez’s report, although a guard indicated in the file that the chaplain had exaggerated what he had witnessed. He was told that the inmate, whose name he did not know at the time, had later been released.