WASHINGTON, July 15 (Reuters) - The U.S. military in many cases does not properly investigate allegations of sexual assault, sometimes failing to collect key evidence, fully examine crime scenes or interview witnesses, a probe by the Pentagon's inspector general found.
The report, which was released to the public on Monday, came as Congress weighs measures that would overhaul how the military handles sexual assault cases after a string of high-profile scandals in the armed forces.
The inspector general's review of 501 criminal investigations in 2012 included cases of rape and aggravated sexual assault.
Although it found some flaws in the investigations 72 percent of the time, it said that they usually didn't have a negative impact on the investigation and that 89 percent of the cases met or exceeded investigative requirements.
However, it flagged serious concerns in 11 percent, or 56, of the cases. In some instances, investigators did not collect key evidence from the crime scene or the victim.
"Witness interviews were not thorough or not conducted," the report said.
Congress is weighing legislation to force the military to change how it addresses sexual assault allegations, in the wake of a series of scandals, including accusations leveled against officials whose job it was to defend alleged sexual assault victims.
A study by the Defense Department released in May estimated that cases of unwanted sexual contact in the military, from groping to rape, rose 37 percent in 2012, to about 26,000 cases, from 19,000 the previous year.
The report released on Monday said its actions led to the reopening of 31 cases for additional investigative work.
It faulted in part policies governing the investigations and said investigators were not always required to collect clothing used during or after an assault and did not always have clear, mandatory directives about what to do at a crime scene. (Reporting by Phil Stewart; Editing by Paul Simao)