By Jennifer Lindgren CBS 11 News | CBSDFW.COMBy Jennifer Lindgren

DALLAS, Texas (CBS 11 NEWS) – Day five of the intoxication manslaughter trial for former Cowboy Josh Brent began with a hearing between attorneys and the judge.

Prosecutors rested their case on Thursday, ending with testimony from two members of the Dallas Cowboys team and the medical examiner.

Before the defense could begin with evidence presentation on Friday, the prosecution objected to the first witness.

Janine Arvizu is chemist, who works as an expert witness.

Brent’s defense team called on Arvizu to present her findings related to the toxicology test — the test performed by SWIFS that determined the level of alcohol in Brent’s blood after the fatal crash.

On Wednesday the toxicologist testified that Brent’s BAC was .189 — more than twice the legal limit for intoxication.

Arvizu says she found many flaws with the SWIFS process of testing BAC.

She says the tube used to collect the sample was 4 mL, instead of 10 mL, that the sample was not properly sealed. She implied that the temperature at which the specimen was stored on December 8, 2012 until December 10, 2012 may not have been the proper temperature.

Arvizu questions the validity of the process, including whether the calibration of the gas chromatograph was correct, and the ethanol in the sample was expired.

Prosecutors did not want Arvizu to testify, and spent an hour Friday morning presenting their case to Judge Robert Burns, III.

Gary McDonald told the judge that Arvizu is a chemist, not a toxicologist, and that her research was speculative and not backed up by peer published studies.

Ultimately the judge determined that Arvizu could testify, but that she cold only speak to the ethanol levels in the blood sample, not the validity of the method for testing or contamination.

Prosecutors will cross examine Arvizu Friday afternoon.  She is the first of an expected four to five witnesses for the defense.

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