ORLANDO, FL --An attorney for a mother charged with killing her 2-year-old daughter suggested Tuesday that a crime scene investigator altered crucial evidence. Casey Anthony's defense attorney questioned crime scene investigator Gerardo Bloise about why he dried out garbage found in a bag in Anthony's car. The bag is important since defense attorneys say a foul odor in the car came from the garbage, while prosecutors contend the smell was from decomposing human remains. "You had no idea it would alter significant items in this case?" defense attorney Jose Baez said during cross-examination. Bloise said he was following protocol, since drying out evidence preserves it and makes it easier to examine. Caylee Anthony's skeletal remains were found in a wooded area not far from her grandparents' home in December 2008. Anthony has pleaded not guilty to killing her daughter. If convicted, she could be sentenced to death. Her defense attorney has said the toddler drowned in the family's swimming pool A K-9 handler also testified that his German shepherd alerted on Anthony's car trunk and also the backyard of the Anthony home during a search for evidence of Caylee in the days after she was reported missing. When deputies opened the car's trunk, the dog jumped forward and placed his paws on the car. He then laid down, indicating an alert, Jason Forgey testified. Forgey then took the dog to the Anthony home where he alerted on an area in the backyard near a playhouse and sandbox, the handler said. Under cross-examination, however, Forgey said when he and the dog returned to the Anthony home the following day the dog did not alert on anything. A scientist at the Oak Ridge National Laboratory returned to the witness stand Tuesday. Arpad Vass, who developed a new technique for detecting decaying bodies, was called back because prosecutors had showed him the wrong can containing the odor from Anthony's car during his testimony Monday. They showed him the correct can Tuesday. During Monday's testimony, Vass described smelling an "overwhelmingly strong" odor of human decomposition in the can containing an air sample from Anthony's car. Vass has pioneered a way of detecting human decomposition from air samples and detailed for jurors his research on the chemical compounds observed when a body breaks down. Until Monday, the tests had never been introduced in a trial in the United States. Vass told jurors the amount of chloroform in the car's trunk was "shockingly high." Chloroform is present during decomposition. An FBI expert on Tuesday appeared to contradict Vass' assertions about the amount of chloroform in the car and said the chemical also is present in common household cleaners. "It was not the most chloroform I've seen in 20 years," Michael Rickenbach said under cross-examination. Rickenbach said he detected amounts of chloroform in Anthony's trunk comparable to that of household cleaners. He also noted the substance is present in water. Rickenbach tested carpet samples from the trunk's spare tire cover and from the right and left sides of the trunk. Rickenbach acknowledged, during later questioning by prosecutor Jeff Ashton, that describing chloroform levels as high or low is subjective.