A Behind-The-Scenes Look At Crash Reconstruction

MINNEAPOLIS (WCCO) -- It's a crime with no witnesses and no surveillance video, but investigators seem confident they know what happened.

Three weeks after the hit-and-run that killed Anousone Phanthavong, prosecutors charged Amy Senser with criminal vehicular homicide.

They're tight-lipped about exactly what evidence they have in this case, but the State Patrol did take WCCO behind-the-scenes to show what it takes to crack similar cases.

After thirty years of reconstructing accidents, there are still numbers that seem shocking, but numbers are the name of the game.

From estimating speeds to using instruments like theodolites, it's a fancy way of using physics and trigonometry to investigate crashes.

"It's hard to disagree with Sir Isaac Newton," explained Sgt. Paul Skoglund of the Minnesota State Patrol.

But beyond the obvious of surveying skid marks and scrapes, there are some clues hiding in places you may not expect.

"Don't ask me how it happens but when people get hit by a car, they usually get pulled right out of their shoes," said Skoglund. "If the pedestrian got pulled out of their shoes, and they were in that crosswalk, that would help us establish where they got hit."

And it's not just human calculations they depend on. You may not know it, but there can be multiple little computers built right into your car. When your speed changes suddenly, these computers can track all sorts of information that troopers can later use.

Skoglund showed WCCO a graph of one vehicle's speed which showed, at about ten seconds before the airbag deployed, the vehicle traveling at 94 miles an hour.

Ultimately, it's science that will decide if there was a mistake made, and whether each incident may require criminal charging.

The sergeant says when presenting their findings to a court, they always try to calculate things within a range, like distances or speeds. They say that's because they acknowledge this isn't always an exact science.