WASHINGTON — When Ferguson, Mo., police Officer Darren Wilson left the scene of the shooting of unarmed teenager Michael Brown, the officer returned to the police station unescorted, washed blood off his hands, and placed his recently fired pistol into an evidence bag himself.
Such seemingly unorthodox forensic practices emerged from the voluminous testimony released in the aftermath of a grand jury decision Monday night not to indict Wilson.
The transcript showed that local officers who interviewed Wilson immediately after the shooting did not tape the conversations and sometimes conducted them with other police personnel present.
An investigator with the St. Louis County medical examiner’s office testified that he opted not to take measurements at the crime scene.
‘‘I got there, it was self-explanatory what happened,’’ said the investigator, whose name was not released, in his grand jury testimony. ‘‘Somebody shot somebody. There was no question as to any distances or anything of that nature at the time I was there.’’
The investigator, described as a 25-year veteran, did not take his own photographs at the scene of the shooting because his camera battery was dead, he said. Instead, he relied on photographs shot by the St. Louis County Police Department.
The medical examiner and Ferguson Police Department did not immediately respond to requests for comment.
When Wilson returned to the Police Department after the shooting, he was permitted to drive by himself.
No one photographed his bloodied hands before he washed up at the station because ‘‘there was no photographer available.’’
Later, injuries to Wilson’s head caused by punches he said were thrown by Brown were photographed by a local detective at the Fraternal Order of Police building, not at police headquarters.
An FBI agent interviewed by the grand jury said he did tape his interview with Wilson. The agent, who was not identified, said Wilson washed up immediately after the shooting because he was worried about the danger presented by some one else’s blood, not about preserving evidence.
‘‘His concern was not of evidence, but as a biohazard or what possible blood hazards it might attract,’’ said the agent, who like other witnesses was not identified by name.
At the crime scene, the medical examiner did not see stippling, the residue of gunpowder on clothing that can indicate shots fired at close range. Eventually an autopsy found evidence of stippling.
In the extended interviews, prosecutors do not come across as particularly aggressive or curious. But they do question police procedures on a couple of occasions, including the failure by Ferguson and St. Louis County investigators to tape their interviews with the officer after the shooting.