An attorney for Benjamin Scott Brewer said there is no proof that the long-haul truck driver was intoxicated at the time of the June 25, 2015, wreck at the Ooltewah exit in which six people were killed.
Jay Underwood of the public defender's office said law enforcement officers saw no sign of impairment and dropped him off for a ride back to London, Ky., hours after the horrific wreck.
District Attorney Neal Pinkston told the jury from Nashville that meth use was "the only explanation" for the massive crash that spread bodies and debris over a 453-foot stretch of I-75.
He said Brewer himself said he did not doze off, and he said there was nothing wrong with the brakes on the Peterbilt.
Brewer, 42, is charged with six counts of vehicular homicide by intoxication, four counts of aggravated reckless assault, DUI and speeding.
The jury will begin deliberating on Thursday morning.
Killed were well-known Cleveland musician Brian Gallaher and Dalton State assistant director of residential life Jason Ramos. Also killed were Tiffany Watts, her mother Sandra Anderson, and daughters Kelsie and Savannah.
Attorney Underwood said, "Of course, it was a bad accident, and we all wish it had never happened. But don't let emotion cloud your judgment."
He said the driver dozing off after a long day behind the wheel was the most logical explanation. He said when first questioned he told of hitting his head, then trying to slam on the brakes. He said Brewer likely was jarred awake when he struck his head, then he was so disoriented that he could not find the brakes.
The attorney said, "He was speeding, but so was everybody else in that stretch." He said a video from the nearby Cracker Barrel showed him going along with the flow of traffic 1,500 feet before the collision.
He said Brewer was charged based on a "rushed, sloppy" blood test. He said the defense only found out late that the test was contaminated.
DA Pinkston said, "The fact that he never hit the brakes is the largest sign of impairment in this case."
He said, "Why would you not brake after you hit the first car? - because he's impaired."
The DA named all the victims and said, "We should not forget them and we should not forget what this man did to so many people."