An expert for former Dallas Cowboys defensive tackle Josh Brent's attorneys won't be allowed to testify about potential contamination of the blood tests used against him.
Judge Robert Burns said Friday that much of laboratory auditor Janine Arvizu's testimony was speculative and wouldn't help the jury.
Brent is accused of drunkenly wrecking his Mercedes in a December 2012 crash that killed Jerry Brown, a practice squad linebacker and Brent's teammate at the University of Illinois.
Brent's attorneys say he was not drunk and accused authorities of making mistakes on blood tests that showed Brent to have a blood-alcohol level more than twice the legal limit.
Arvizu said the crime lab used the wrong tubes and contaminated the sample, but Burns said he wasn't convinced her testimony had scientific basis.
In court Friday, Arvizu did testify about the accreditation of Dallas lab and calibration of equipment.
On the stand Arvizu said the lab's equipment calibration was unreliable, she said equipment was calibrated weeks before Brent's blood sample was run and that it was unusual to see a lab that did not calibrate equipment daily.
While Brent's blood alcohol test was .18, twice the legal limit, Arvizu told the jury the test was unreliable. Arvizu said the Dallas testing procedure in Brent's case did not follow standards that are extremely common elsewhere.