The final report follows a preliminary one released earlier this year.
Sandra Allmond, 55, and 11-year-old Taylor Strange died when Allmond made a left turn into the path of Trooper J.D. Goodnight on Interstate 85 Business Loop at the River Road intersection in Jamestown on May 23.
According to the report, Goodnight said in a statement that he was traveling southbound on 85 before the crash and clocked a vehicle traveling northbound at 80 mph in a 55 mph zone with his radar system. He activated his blue lights and turned around headed north.
Investigators said Goodnight reached speeds of 120 miles an hour in pursuit of the vehicle as he approached the intersection with River Road, but slowed to 95 before he hit Allmond's car.
The report has statements from several witnesses - some of whom contradict one another.
Floyd Ross of Winston-Salem said he was behind Allmond headed north and saw her get a green turn signal at River Road before she began her turn. He saw Goodnight's cruiser with its blue lights activated, but he did not hear a siren before the impact.
In his statement, Goodnight said he activated his blue lights, but did not activate his siren because it would have forced him to look down - which he said he did not want to do for safety reasons.
Eyewitness Terry Johnson's statement is also included in the report. He told ABC11 in an interview earlier this year he didn't see a speeder and that Goodnight didn't turn around to chase one.
He said that he was headed south in the right-hand lane of 85 when he saw a Highway Patrol cruiser parked in a paved turnaround area.
With his speedometer reading 55 miles per hour, Johnson looked in his rear view mirror.
"This trooper leisurely pulled out - into the right hand lane - and began to follow me. I wasn't gaining on him," said Johnson. "He was not gaining on me."
Even as the two came to sign for an upcoming traffic light warning the intersection was 1000 feet away, Johnson said he recalls he was still doing the speed limit.
"All of a sudden, he jumped from behind me and I couldn't believe how fast he got that car going as he went by me," he recalled.
Johnson said Goodnight veered from the left lane at the River Road intersection into to the right lane to avoid Allmond's car as she turned in front of him but couldn't.
Two other witnesses contradict Johnson. Theodis Duff of High Point said he saw the speeder Goodnight turned to chase and that is passed him at a high rate of speed before he came up on the crash.
Michael Wayne Perry of Thomasville also said he saw the speeder and that Goodnight had a green light before he hit Allmond's car. Perry said at the time of impact, the speeder's car was visible further up the road.
In the final report, the Highway Patrol says testing was done at the intersection to see if Goodnight's car would have been visible to oncoming motorist. The report concludes it would have been given light conditions that day.
The report also throws doubt on Ross's statement that Allmond had a green turn signal before the impact. Investigators say there is no indication of a signal malfunction, and other witnesses said Goodnight had a green light before the crash.
The reports concludes that Allmond caused the crash by turning in front of Goodnight. It said Allmond required glasses to see properly, and while glasses were found in her car, it's not known if she was wearing them.
While the report blames Allmond for the crash, it says Goodnight's speed "contributed to the severity of the collision."
It also says:
"Had Trooper Goodnight been operating his vehicle's siren on this occasion, it may have provided an audible warning for motorists in the area."
A second investigation of the crash was done by the North Carolina Attorney General's Office in anticipation of potential lawsuits against the state. The AG's report is done, but it says it won't release its findings.
There were two children in the backseat of Allmond's Honda at the time of the crash. Allmond's grandson, 11-year-old Elijah Allmond, and Taylor's cousin, 9-year-old Steven Strange, were hospitalized, but are now back with their families.
Trooper Goodnight was also hurt. He has since returned to duty.