The only thing the defense could get in rebuttal was that the CSI tech didn’t “test” every object available at the crime scene residence. Its a hint that the CSI could have missed some exculpable evidence usable for the defense’s case. That’s weak but not an uncommon strategy.

http://thechronicleherald.ca/canada/1335488-forensic-expert-at-trial-for-couple-accused-of-abuse-says-he-found-hair-in-tape