The Trump administration has lost or abandoned hundreds of criminal cases against protesters and immigrants, a Times investigation found.

In its nationwide immigration crackdown, the Trump administration has charged hundreds of people with assaulting or impeding federal agents. President Trump has branded them “insurrectionists,” “animals” and “thugs,” part of a broader effort by his administration to cast protesters and immigrants as violent criminals.

But a close examination of those cases reveals that in its rush to meet White House demands for deportations, federal law enforcement has engaged in extensive misconduct — ranging from attacking protesters to destroying evidence and misrepresenting facts in court.

The New York Times found that the Trump administration has filed assault charges against more than 550 people who were caught in its immigration dragnet — far more than previously known. Of the more than 400 cases resolved so far, nearly half have unraveled: Juries acquitted defendants, judges threw out charges, or prosecutors withdrew them.

The record is abysmal by the typical standards of federal prosecutions: The Justice Department seldom loses criminal cases, with more than 90 percent of defendants pleading guilty or being convicted at trial.

The Times obtained court filings for every assault case and reviewed hearing transcripts, interviewed witnesses and federal officials and watched videos of dozens of encounters that led to criminal charges. The review, the most comprehensive to date, suggests that the administration’s use of the law has often been less about protecting federal agents than about providing legal cover to cow protesters and immigrants into submission.

“There seems to be a pattern of charges being filed without any merit,” said Jimmy L. Arce, a former federal prosecutor in Chicago who served on a commission that investigated immigration raids in the city last year. He added that some defendants were “having their speech criminalized by the U.S. attorney’s office.”