From a corridor outside the intake bays at the Allegheny County Medical Examiner’s office, chief examiner Karl Williams takes a mental inventory.
"Thirteen-hundred cases, 1,600 items in every year, around 150,000 tests," he said. "You can’t do analyses of every piece of potential evidence you get in, but we’ve always got it."
Homicides committed outside city limits make up just a fraction of the deaths Williams’ county-wide office oversees, but most murders are evaluated in tandem by multiple agencies, including county and municipal police, pathologists and a spectrum of other agencies tasked with a battery of supplemental tasks.
Scott Smith, special agent in charge of the FBI’s Pittsburgh office, said his agency has helped smaller, local police forces a lot over the years, usually when a crime involves three or more casualties. Smith's officers build criminal profiles, interview witnesses and collect and analyze forensic evidence.
“Mostly in the scientific areas," he said. "More recently though, it could involve in the cyber-forensic, any kind of digital evidence. Sometimes local departments aren’t as established in the review of some of the current technology that’s found at crime scenes, so we offer a lot of assistance there.”
County spokeswoman Amie Downs said any of two dozen agencies could be working together on the same case at the same time.
In the case of the Wilkinsburg shooting that killed six and injured three others last week, that roster of investigative talent includes the FBI, the Wilkinsburg Police Department, the federal Bureau of Alcohol, Tobacco, Firearms and Explosives and the lead agency, the Allegheny County Police.
"They have also been provided support by other organizations and agencies as needed," Downs said in an email. "They’re often just not publicly listed."
So who takes charge? That depends.
In January of 2012, Arthur Lamont Henderson raped three women in three days, spawning an investigation shared among Ross and Hopewell townships, Allegheny County, state police and others.
Williams' team tested a wealth of evidence, and Ross Township Detective Brian Kohlhepp helped bring Henderson in. Kohlhepp worked with county officials on that case and national agencies on others.
Good solid footwork, Williams said, led to high-quality DNA samples from offenders and victims. His analysts helped turn the case in a matter of days, he said, because everyone efficiently communicated their needs.
"There's a really nice collegial attitude between all the (police) forces in Allegheny County," Williams said.
He said he needs that spirit of goodwill. Of the 104 police jurisdictions in Allegheny County, each investigating officer is required to log potential evidence into a secure, online database that issues a unique barcode to every item.
"Once they bring it down to the office, chain of custody begins and at any point, they can go in and see what's happening with their evidence," he said. "We don't issue written reports. We don't issue faxes. Everything is online for them as they are examining their evidence."
Take a gun recovered from a scene, Williams said. It may need to be fired for ballistics testing, dusted for prints and tested for trace amounts of DNA.
“So when a police agency goes into the system, they can see that the gun’s downstairs waiting to go upstairs," he said. "They can see it when it goes upstairs to ballistics, back upstairs to serology for DNA – because that’s what you need. In order to take that evidence into court, you have to have an absolutely immaculate chain of custody.”
While the evidence makes its way through the system, Williams said investigators need detectives talking to witnesses and piecing together details of the homicide that he can't glean from science alone.
"It’s a sophisticated community, but it still is small town in some ways – people knowing each other (and) working with each other," Williams said. "There are a lot of law enforcement agencies, and we work as seamlessly as we can with all of them.”