An expert witness called by the prosecution testified on Wednesday that former Dallas Cowboys defensive tackle Josh Brent has been drinking heavily before crashing his new Mercedes in December 2012, killing teammate Jerry Brown Jr.

Toxicologist Justin Schwane told the court he tested three vials of Brent's blood taken at the time of his arrest and said that, based on blood alcohol calculations for a person as large as the football player, Brent likely consumed 17 standard size drinks.

Schwane took the stand for nearly six hours and faced a long cross-examination from defense attorney Deandra Grant, who questioned him over whether he improperly stored the vials, which could affect the results.

"I saw nothing that made me think it was unsuitable for analysis," Schwane said.

Brent's blood alcohol level was 0.189, according to police documents. The legal limit in Texas is 0.08. He is charged with intoxication manslaughter and could face up to 20 years in jail, if convicted.

Brent's lawyers said in opening arguments at the Dallas County court on Monday their client had made a terrible mistake but was not intoxicated when he got behind the wheel.

Defense attorney George Milner told the court that the amount of liquor Brent drank before getting behind the wheel was not enough to make him drunk because of his large build. Brent's playing weight was 320 pounds (145 kg).

In other testimony on Wednesday, Irving police officer James Fairbairn, who investigated the crash, told jurors Brent's car was traveling around 110 miles per hour, in a 45 mph zone, when it struck a curb on the highway.

The vehicle went airborne and smashed onto the pavement before catching fire.

Later this week, Dallas Cowboys safety Barry Church and defensive back Danny McCray, who had been drinking with Brent and Brown at a Dallas club before the crash, are expected to testify.

Brent, 25, was put on leave from the Cowboys after the accident and retired in July.

The trial is expected to take as long as two weeks.