leaving his shoe impression? >> the theory of any crime scene investigation is that the suspect is always going to leave something of themself at the scene or take something away that's going to link them to the crime. >> the shards were collected and sent to the forensics lab. >> glass is such a smooth, perfect surface that it's really the best surface we can possibly hope for to get a footwear impression on. >> the linoleum floor was dusted with a powder called aurora pink that sticks to any moisture present. then, using what is called an alternate light source, any powder that clings to the moisture will fluoresce. >> if you have a patterned linoleum where the background is interfering with the impression, you can usually use your alternative light source to eliminate the background, and then the fluorescent powder that you use to dust up the impression is very bright and so it makes a very good contrast.