Original sentence: Investigators can use DNA located in blood, semen, or hair left at the scene to identify a possible suspect.Many jurisdictions require convicts of certain types of crimes to provide a sample of DNA for inclusion in a computerized database.This has helped investigators solve old cases where the perpetrator was unknown and only a DNA sample was obtained from the scene (particularly in rape cases between strangers)
Edited sentence: A very common way is to identify a blood sample found where the crime took place.As a result of this, it is possible to find DNA belonging to someone that in actual reality never was there when the crime took place.DNA happens to be easily transmittable, by for example, a handshake.This is why some people have been judged guilty for a crime they did not commit, even though DNA tests showed otherwise