The coefficient of friction varies slightly with how wet the surface is, so it, and all subsequent calculations are best when confined to dry surfaces, and most roadway surfaces require 3000 pounds of force to slide something on them. In the basic speed skid formula, S is the skid distance, V is the velocity or mph, and f the coefficient of friction. Again, this results in a fairly conservative estimate of the minimum speed of the vehicle, but it has held up in court well. Some skidmark experts will go further and conduct their own test skids in close cases. When known facts are entered into a computer, the computer can then generate conclusions based upon assumptions in the software being used.
Animations are one form of forensic reconstruction.
Other forensic experts have been doing reconstructions for years, to try to figure out what a disappeared person would look like after 10 years, for example. Other times it's a full motion video simulation. A simulation often involves the mathematical capability to project different possible outcomes of what happened. Forensic computer animations are subject to strict discovery and disclosure rules. It must also be determined that probative value outweighs prejudicial effect.