Some crime investigations turn on eyewitness accounts.
Others are made through lingering fingerprints or blood specks.
Here's a case of violent road rage that authorities say was untangled when police tracked shards of window glass that had shattered off a suspect's car.
According to court documents and the office of Suffolk District Attorney Daniel Conley, this is how Boston police detectives pieced together a late-night episode last month that began with a double-stabbing over a parking dispute in Allston, left tinted glass fragments in Chestnut Hill, and ended with the arrest of a suspect from Dorchester.
It was in the wee hours of June 8 when four men in their 20s, from Brookline and Dorchester, were chatting near a parking area by the always hectic corner of Commonwealth and Harvard avenues.
A gray car that looked to witnesses like a Dodge Intrepid tried to turn in to the lot, but the group was in its way. Words flew back and forth. The gray car pulled away.
Soon, the foursome hopped into their
"That's him, that's him," one of the Dodge's crew said, according to the police report, alluding to the earlier showdown.
The group got out of the Explorer to confront the hecklers. Things turned nasty.
The Dodge's owner allegedly circled the group, saying "You better know karate," and "Someone is going to leave in an ambulance."
Then, more than the verbiage turned cutting.
The Dodge's owner allegedly produced a knife, and started slicing one victim in the upper body, forearms, and shoulder, and another in the back and arm.
For good measure, he or a member of his entourage allegedly took the knife and punctured the rear tires of the Explorer.
Then he ran off toward his car. One of the victims was in hot pursuit, but was allegedly brushed aside by the Dodge.
Meanwhile, the other stabbing victim joined in to help. Brandishing a golf club pulled from his car, he swung and struck the rear window.
The Dodge kicked into reverse, and allegedly smacked the guy holding the golf club. Then it sped off up Comm. Ave. toward Newton. At 2:32 a.m., two Boston police officers out on patrol were flagged down by a cab driver. He told them there'd been a fight.
The cops found one of the stabbing victims stumbling around, dazed and bleeding from both arms. One of his friends gave police details about the run-in.
Though the injuries were not considered life-threatening, the cops summoned an ambulance. They also broadcast a description of the car and the main suspect, a man in his early 20s wearing a white T-shirt.
Though the victims and witnesses didn't catch the license plate, they described a gray Dodge Intrepid with chrome rims and crushed, tinted glass.
Hours later, and about 5 miles away, Newton police discovered a patch of chipped glass in a parking area of the Mall at Chestnut Hill. The glass had a dark filmy tinge to it. Newton police said they could not comment on how they came upon the glass because the incident is now the subject of an ongoing court case.
Newton cops, alerted by the radio call, notified Boston police, who took control of the serrated evidence.
Figuring the desperado in the Dodge eventually needed to get his car fixed, the cops started dialing up area auto glass repair shops, many of which are centered around the Dorchester Avenue commercial strip.
They were looking for a gray Dodge or similar vehicle that had recently sustained damage to its tinted rear window.
At the sixth place they called -- Fields Corner Auto Glass -- they hit pay dirt.
Just that morning of June 11, the cops were told, a guy had brought in a gray sedan and wanted to replace its smashed rear window. It was a Chrysler 300 with chrome rims. And shredded tinted glass.
After comparing the glass with the remains found at the Chestnut Hill mall, Boston police say they traced the car to a 26-year-old man from Dorchester named Richard Wallace, and arrested him.
Police say they buttressed their case when one of the stabbing victims was shown an array of photos and picked Wallace as the one who'd allegedly attacked him.
On June 25, Wallace pleaded not guilty in Brighton District Court to charges that included armed assault with intent to murder. He made $10,000 cash bail, and last week a relative at his home said he was out of the country and on vacation. Wallace is due back in court July 25.
The victim who wielded the golf club was not charged. Authorities say the 22-year-old -- whose off-the-links swing gave cops a chance to take the investigative offensive -- was acting in self-defense.
Ric Kahn can be reached at email@example.com.