Police Chief Joe Mokwa also said at a news conference Friday that the 29-year-old Hancock was speaking on a cell phone at about the time of the crash early Sunday on Interstate 64 in St. Louis.
"Mr. Hancock was legally intoxicated at the time of the accident," Mokwa said.
St. Louis medical examiner Michael Graham said Hancock's blood-alcohol level was 0.157, nearly twice Missouri's legal limit of 0.08.
Mokwa said 8.55 grams of marijuana and a glass pipe used to smoke marijuana were found in the rented Ford Explorer. Toxicology tests to determine if drugs were in his system had not been completed.
An accident reconstruction team determined Hancock was traveling 68 mph in a 55 mph zone when his SUV struck the back of a flatbed tow truck stopped in a driving lane. Mokwa said there was no evidence Hancock tried to stop. He did swerve, but too late to avoid the collision.
Graham said the pitcher died instantly of head injuries. Hancock was not wearing a seat belt, but Graham said the belt would not have prevented his death.
Mokwa said cell phone records showed Hancock was speaking with a female acquaintance at about the time of the accident. Mokwa said the conversation ended abruptly, presumably when the accident occurred.
It was the second time in less than five years that a St. Louis pitcher died during the season. Darryl Kile was in 2002.
Three days before Hancock's death, the Cardinals got a scare that some teammates said reminded them of Kile's death — Hancock overslept and showed up late for a day game in St. Louis. Hancock told the St. Louis Post-Dispatch he thought the starting time was later and didn't get up until the "20th call" from anxious teammates.
"We were all a little nervous," closer Jason Isringhausen said earlier this week. "We don't care if you're late. That happens. We want to know that you're OK."
Hancock, a key member of the bullpen on the Cardinals' World Series championship team from 2006, was driving alone. The tow truck driver was not hurt.
The Cardinals played a day game Saturday, losing to the Chicago Cubs. Hancock left Busch Stadium around 6:30 p.m. and arrived about two hours later at Mike Shannon's, a restaurant and bar owned by Shannon, a former Cardinals third baseman and the team's broadcaster.
Hancock left Shannon's shortly after midnight.
At 12:34 a.m. Sunday, the tow truck came upon the disabled Prism and stopped behind it with its yellow lights flashing to protect the car, Mokwa said. A few moments later, Hancock's SUV struck the rear of the tow truck.
"If you drink, don't drive," Mokwa said. "Use a taxi. Have a designated driver. Call a friend."
Graham said Hancock suffered head injuries so severe he died "within seconds." He also suffered severe chest injuries.
"There's nothing at all that could have been done for him," Graham said.
An estimated 500 mourners turned out Thursday for a memorial service for Hancock in Tupelo, Miss., recalling the pitcher as a good-hearted prankster. Among the mourners were Hancock's teammates, coaches, manager Tony La Russa and general manager Walt Jocketty. Hancock was buried Wednesday in rural Itawamba County, Miss.
Hancock, who pitched three innings of relief in Saturday's 8-1 loss to the Cubs, made his major league debut in September 2002 and played for four major league clubs. He went 3-3 with a 4.09 ERA in 62 regular-season appearances for the Cardinals last season, leading the bullpen in innings, and pitched in three postseason games.
He was 0-1 with a 3.55 ERA in eight games this season.
Hancock joined the Cardinals in spring training last season after Cincinnati released him for violating a weight clause in his contract. He also pitched for Boston and Philadelphia.
The Cardinals postponed a home game the day of the accident against Chicago and haven't won since. They were swept in a three-game series in Milwaukee and had an off day Thursday.