Felix Adatsi, a supervisor with the Michigan State Police crime lab in Lansing, used an overhead projector and whiteboard to explain how he determined Ruh's blood-alcohol level when Ruh crashed his truck on the evening of Dec. 12, 2009.

Ruh's 7-year-old son, Robert Ruh III, died in the crash, and his son Austin Ruh, who was 8 at the time, was injured.

Blood taken from Robert Ruh II more than two hours after the crash showed he had a blood alcohol content of 0.07, below Michigan's drunk-driving threshold of 0.08.

Adatsi said he used a process known as retrograde extrapolation to determine Ruh's blood alcohol level was between 0.08 and 0.10 at the time of the crash.

The process takes into account factors such as an individual's weight, gender, what time he stopped drinking and whether he had eaten, Adatsi said.

A range was calculated because it was impossible to know how much beer had been absorbed into his bloodstream after Ruh consumed it around 6 p.m., Adatsi said.

Defense attorney John Vincent questioned the usefulness of the process, since it relied on scientific averages and inexact figures.

Adatsi testified that some toxicology experts put less faith in retrograde extrapolation because of those variables, but more agree with it than disagree with it.

Two men who live near the accident scene along U Drive South near 29 Mile Road in Homer Township also testified Wednesday.

Teddy Koons and Levi Schwartz both said they heard a vehicle drive by at a fast speed shortly before the accident, and that the road that evening was icy in parts.

"I remember thinking, 'Wow, he's going fast and there's ice in front of the woods,'" Schwartz said.

He and Koons both said they smelled alcohol on Ruh when they got to the accident scene.

Schwartz said he helped Ruh get out of his vehicle, but it appeared that one of the boys stuck in the truck was already dead.