CHATTANOOGA, Tenn. (AP) — The trial of a truck driver charged with killing six people in a 2015 interstate crash has been postponed for the second time this year.

The Chattanooga Times Free-Press reports Hamilton County Criminal Court Judge Don Poole postponed Benjamin Brewer's trial date after attorneys debated over a potential witness Tuesday and expressed uncertainty over their preparation for the Sept. 25 start date.

The first postponement came in June, following the revelation of a retest of Brewer's blood that found a lower amount of methamphetamine in his system.

The debate Tuesday among public defenders, state prosecutors and government attorneys hinged on deposing the federal employee who oversaw that retest.

Attorneys are due to return to court Oct. 17, but it's unclear if they'll pick a new date then.

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Information from: Chattanooga Times Free Press, http://www.timesfreepress.com