There are many crimes that implicate different instruments that can leave contact traces. For making a felony against patrimony, such as theft, housebreaking or destruction, the offender needs instruments to get in certain polices or areas by forcing or breaking the objects that block the access to those areas. The felons can use simple instruments like those for material processing or they can use instruments that they built. The forensic expertise of instruments traces can figure out the nature of type of instrument they used, the mechanism of the breaking and succession of facts for accessing a patrimony. The expertise can also say if there were one or more instruments. Analyzing the mode of operation and the procedures used during the crime, the expertise can determine the number of persons involved in the felony.