Casey Anthony murder trial enters Day 27 in Fla.

By the Associated Press | June 23, 2011 | 3:59 AM EDT

Casey Anthony sits alone at the defense table before the start of court in her murder trial at the Orange County Courthouse in Orlando, Fla. on Wednesday, June 22, 2011. Anthony is charged with first-degree murder in Caylee's death and has pleaded not guilty. (AP Photo/Red Huber, Pool)

ORLANDO, Fla. (AP) — The Florida murder trial of Casey Anthony, who's accused of killing her 2-year-old daughter, resumes a day after the defense continued trying to poke holes in some key prosecution forensics evidence.

The defense case enters its seventh day Thursday.

Forensic chemist Michael Sigman had collected and tested air samples from the trunk of Anthony's car in July 2008. Sigman testified Wednesday that he couldn't say for sure there was a body inside it based on his analysis.

Sigman was one of five forensic witnesses to testify Wednesday as the defense continued to attack the prosecution's contentions that Caylee Anthony was suffocated with duct tape and placed for some time in the trunk of her mother's car.

Casey Anthony is charged with first-degree murder. She's pleaded not guilty.