Drug Facilitated Crimes is an emerging discipline in the field of forensic toxicology. The most widespread DFCs are Drug Facilitated Sexual Assaults (DFSA); sexual crimes which occurred with involvement and administration of drugs. Drugs such as flunitrazepam, lorazepam, GHB, nitrazepam, midazolam, temazepam, ketamine are added to the food/drink of the victim during any party, or at the bus stands or railway stations without the knowledge of the victim and inhibits person’s ability to resist and prevent her from remembering the assault. These drugs being depressants in nature cause symptoms of drowsiness, impaired perception, nausea, vomiting, unconsciousness, anterograde amnesia and mislead the police to form an assumption that the person has only drunk and not drugged. The metabolism of these drugs is too rapid and the drugs get excreted from the body before the incident is reported to the Police Officer. These fast-acting drugs therefore leads to various problems in the detection and analysis of drug facilitated crimes. The paper focuses on such problems and challenges associated with these drug facilitated sexual assault cases.