The following are excepts from a Car & Travel article titled "CSI:BQE Crash Scene Investigators on our Roads", which was predominantly based on an interview with Grahme Fischer.

from Tales Tires Tell:

To a trained analyst, tire marks can reveal points at which a vehicle braked, accelerated, or changed directions. On a curve, tires leave characteristic impressions - "yaw marks" - that can even offer clues to the vehicle's speed at that point. And you might find them 100 feet or more from the eventual point of impact.

"Tire marks don't live forever," explains Grahme Fischer, president of Technical Problem Solvers, Inc., and a director of the New York State Traffic Accident Reconstructionists Society (NYSTARS). "Most disappear within a month. In the city of New York, you might see 10 spurious marks for each collision." The faster investigators get to the scene - and the more isolated the location - the better.

from Who Was Driving?:

Investigators pore over other evidence as well. For example, if a crash involves fatalities, the victims' clothes may offer clues. "Clothing will often pick up plastic content from the seats or dashboard or other interior surfaces," explains Fischer. "And seat belt material may transfer as the belt is stretched." Characteristic stretch marks on a safety belt, impressions left on an occupant's body and even blood splatters can help determine people's positions in the vehicle.

from Lessons Learned

"Everyone who has worked in this office for two months or more wears a seat belt, whether or not they wore one before they started," says Fischer. "Personally, I also avoid driving near or directly in front of big trucks. I avoid them with the knowledge that a significant fraction of trucks have maladjusted brakes, and they're not capable of stopping nearly as well as they should. I've seen the mayhem that can result. Let's just say I don't stay in front of big trucks for long, and when I pass them, I do it in a hurry."

Fischer also carries a camera in his glove compartment, and he recommends every driver do the same. "One of those cheap, throw-away cameras is perfectly adequate," he says. If you're ever involved in a collision - no matter how minor - he recommends taking photos of the vehicle on all four sides, close-ups of the damage (or lack of damage), and features of the roadway.

"There is a small percentage of people who are in the business of creating the impression of injury," he says. "Or they simply believe that because they've had an accident, someone should pay. What you think is an inconsequential collision may turn into a lawsuit six months later. The apparent lack of severity at the scene is no indication of how serious it may become. And photos provide the best objective evidence."

from Hunting Down the Truth

Fischer remains firmly convinced that his profession contributes to traffic safety. "I certainly believe that economic pressure from lawsuits provides an incentive to manufacturers to design safer cars," he says. "Accident reconstructionists make a big difference in product liability cases in which manufacturers did not implement appropriate safety measures."

...Technical Problem Solvers' Fischer heard a prominent anthropologist speak about the perfect job for which humans are adapted. "He said that you would go out hunting, searching for animal tracks," explains Fischer. "You'd find them, follow them and come upon an animal. You'd kill it, then bring it back to the village, and everyone could eat."

"So the perfect job involves working independently, using your intelligence, relying on your senses and using your physical skills," continues Fischer. "Basically, this anthropologist was describing detective work. I think I have that job."