Forensic science is the application of scientific knowledge to solving crime. There are a number of scientific disciplines that can apply to crime, and the associated technology that comes with those disciplines is also made a part of the investigation. What technology is appropriate depends on what sort of science is being used, and what type of crime was committed.
One of the most notable types of technology used in forensics is DNA typing. A person's DNA is unique to them in a way that's similar to a fingerprint, and if their DNA can be recovered from a crime scene then it can help identify suspects as being present at the scene. DNA can be taken from blood, semen or other bodily tissues and fluids. Pathologists and medical personnel tend to be the ones to type DNA and to work with these types of samples to help identify criminal suspects.
There's an entire branch of forensic science that deals with computers. Computer forensic technicians will go through a computer that has been confiscated, break through the security on it and extract information from the hard drive that can be used to provide clues to crimes. Even if emails or documents are "deleted" from a computer, a forensic technician with a specialty in computer sciences might be able to put part of the data back together and to provide investigators with critical information.
A number of different chemicals and chemical processes are also used in forensic sciences. Luminol sprays, which can reveal blood and semen when put under an ultraviolet light, are common tools among crime-scene investigators. Drug-identification processes also are crucial for letting police identify whether or not what they found at a scene was a bag full of flour or cocaine with scientific certainty. Paint matching, whether the paint comes from fingernails or from a car door, is also a chemical process used by forensic technicians.