If you are interested in using laboratory analysis to help solve criminal cases, then consider a career in forensic chemistry. As a forensic chemist you will use knowledge from chemistry, biology, materials science, genetics and criminal justice to evaluate material evidence related to crime scenes. The results of a forensic chemists work are used in police investigation and court trials. 

Most forensic chemists work in government labs for federal, state, local police department, county medical examiner’s office, forensic services lab or a branch of the Federal Bureau of Investigation. However, there are private labs that also provide forensic services and analysis.

American Chemical Society: http://www.acs.org/content/acs/en/careers/college-to-career/chemistry-careers/forensic-chemistry.html