CHATTANOOGA, Tenn. — A Kentucky trucker sentenced to more than five decades in prison for a crash that killed six is seeking a new trial, with defense attorneys arguing the state of Tennessee concealed crucial evidence.

The Chattanooga Times Free Press reports 42-year-old Benjamin Brewer's attorneys want information on a chemical the Tennessee Bureau of Investigation added to his blood sample, asserting they'd never heard of the "contamination" until witness testimony.

Citing that and a second test showing lower levels of illegal drugs in Brewer's system, his attorneys say he should be acquitted or given a new trial. They've subpoenaed prosecutors for communications with the TBI about the substance.

Prosecutor Neal Pinkston says the defense hasn't proven the materials sought are relevant. TBI spokeswoman Leslie Earhart says the chemical didn't affect test results.