The application of molecular genetics technologies to the forensic field is becoming very important, demonstrating a pivotal role in cases that have to do with civil and criminal law, family law, as well as in cases of catastrophes with numerous victims. This chapter aims to analyze the molecular techniques applied to the human and nonhuman forensic scenario, considering the scientific progress from the past 30–40years which has highlighted and continues to highlight the role of the important tool to solve forensic casework. The molecular techniques meet the human forensic fields in several criminal investigations, with completely different tasks. Considering that the drug assumption has direct consequences both for metabolism responses and by the target organs, emerging genetic tools, like epigenetic applications, could be very useful in the forensic sciences. Pharmacogenetics is the study of inherited genetic differences in drug metabolic pathways, which can affect individual responses to drugs, both in terms of therapeutic effect and in terms of adverse effects.