No. He is an investigative journalist; The Cold Cases reads and explains forensic reports but does not perform laboratory analysis.
No. DNA can indicate whose material is present but rarely shows how or when it arrived, since transfer can occur innocently.
Firearms comparisons can be useful, but scientific reviews urge caution about how firmly conclusions are expressed, so method and limits matter.
Sometimes. Retained samples may be retested with newer methods, though results depend on storage, sample condition and laboratory capability.
Consider it when key findings conflict, rest on a single test, use since-questioned methods or lack documentation, and discuss options with qualified experts.