How does a forensic engineer use the law of conservation of energy in a crash investigation

Law of conservation off energy states that energy can neither be created or destroyed and that it can only be converted from one form to another. In the case of crash of two bodies in motion, kinetic energy is converted to distortion and displacement of the bodies, sound and heat. From the results of crash (that is distortion, displacement, heat and sound), a forensic engineer investigating the crash can work out the initial kinetic energies of the bodies and thus estimate the direction and velocity in which the bodies were moving before collision.