Tyree Wright and his younger brother, Emmanuel Johnson, sat in front of their mother's place, 1701 E. Federal St. It was about 10:30, and the street lamp in the narrow alley next to their house spread light over the trash and cracked concrete.
Their uncle was with them. So were their stepfather, his brother and sister-in-law. Their mother was in the house.
They were just talking, hanging, they would remember, when their uncle, David Michael Brown, yelled. He was the first to see it.
"He got a gun," Brown shouted.
Two men walked out of the alley, one aiming a silver-colored revolver at the crowd. Then came the shots. Emmanuel and his uncle jumped away from the steps and ran. Others sped away in a car.
Witnesses said the gunman was aiming at Tyree Wright.
"Me and my uncle started running down the street," Emmanuel later testified. "I turned back around to look for my brother and I seen my brother laying on the ground."
He was face down, according to witness accounts. Blood pooled beneath him. His glasses were beside his head. Police cars and flashing lights swarmed the narrow road. Tyree's mother screamed. A crowd pushed its way toward the body.
"There was a lot of chaotic behavior," Officer Donavan Cox testified.
He asked Emmanuel what had happened. The eighth-grader was frantic, the officer recalled later, even hysterical. But he responded, saying two men had come out of the alley to shoot his brother. One, he said, wore a gray tank top.
Emmanuel told the officer he didn't recall anything more. He said he hadn't seen either man's face. Cox relayed the description across his radio. Gray tank top. It wasn't much. It seemed like half the city was wearing tank tops that night.
But the police would be looking for something else when they found their suspect - gunshot residue.
Cloud of particles
Look through a microscope at the hands of someone who has just fired a gun and there will probably be hundreds of lead, barium and antimony particles. This is gunshot residue.
The same explosion that forces out the bullet also releases these particles in a fine, nearly invisible cloud. It is one of the few ways these three elements become fused.
But after a few moments, much of the residue won't be there any more. It is like talcum powder. One shake and particles scatter. One rub and they'll transfer from a gunman's hands to his pants or a car seat or even handcuffs.
That is why officers try to test a suspect for gunshot residue as soon as possible: It is easy for someone to get rid of it.
Not a `clear result'
It's also why defense attorneys and many experts worry about contamination, and why some departments don't bother with the science. Gunshot residue, they say, can mean someone fired a gun, or was next to a gun, or touched a person who fired a gun, or touched a car seat where someone who fired a gun once sat.
"We feel that for the amount of effort you're putting into it, you're not getting a clear result back," said Elizabeth Ziolkowski, a senior criminalist with the Boston Police Department.
There are few comprehensive studies of how easily gunshot residue transfers. One internal test by the Los Angeles Police Department found that police cruisers were contaminated by gunshot residue and that the particles transferred onto people who hadn't fired anything.
Baltimore has had its contamination issues.
In 2001, the Baltimore Police Department revealed that there had been active firing ranges inside some precinct houses where suspects were tested for gunshot residue. Testing revealed gunshot residue in interview rooms, on tables, on chairs, in the air.
Suspects' hands bagged
The department says it revamped its testing process when it found out about the problem. It set up a "clean" room in a garage area outside of police headquarters for gunshot residue testing. Officers were told to bag suspects' hands at the time of arrest so that they would not be contaminated.
"If they don't bag them, we don't test them," said Koch, the crime lab director.
But it is unclear from internal police documents when this policy went into full effect or whether it has been followed consistently.
Moreover, when staff tested the "clean" room in November 2003 - part of an effort to secure accreditation for the city's police laboratory - they found gunshot residue all over the handcuffs, gun belt and holster of the officer assigned to the examination area.
The results of that test were reported internally in March 2004. Two months later, forensic supervisor Sharon Talmadge issued a mandate to her staff:
"As of todays date (5/14/2004) Police Officers assigned to the Mobile Unit WILL NOT perform GSR testing," she wrote in an e-mail.
The test results also showed dozens of particles consistent with gunshot residue on door handles, chairs and walls. A "unique" particle - the fused barium, antimony and lead distinctive of gunshot residue - was on the floor.
"You've got a contaminated room, obviously," said Taylor, the California expert.