Forensic Science

Forensic science is the scientific method of gathering and examining information about the past. This is especially important in law enforcement where forensics is done in relation to criminal or civil law, but forensics are also carried out in other fields, such as astronomy, archaeology, biology and geology to investigate ancient times. Many challenges in forensic science have to do with determining the likelihood that two fragments of evidence came from the same place or were part of the same object. Scientific techniques, most of them optical, make the adage “crime does not pay” more and more true. Optics is of course used in the first place through imaging of the crime scenes. Much more than simple imaging can obviously be performed. UV light is often used to detect fluorescent semen, vaginal fluids, urine, sweat or saliva. Blood absorbs all UV wavelengths without fluorescing and can, on the contrary by visualized as a black spot on a bright background. Using IR spectroscopy allows for much higher sensitivity of blood stain detection. Raman spectroscopy can be an alternative especially samples immersed in water, since water is a weak Raman scattering medium. Raman scattering is in general weak and can be easily masked by fluorescence. Surface-enhanced Raman Spectroscopy, SERS, is an efficient technique to strongly increase the sensitivity and can be used with extremely small volumes: even single molecules can be detected when attached to metallic nanoparticles (plasmonic enhancement). There is a big potential for the development of hand-held photonic instruments to be used directly in the field. However, courts are rather conservative and the technologies need to be shown absolutely reliable especially when used by non-scientists.