Minute traces of a homemade explosive that was used in the first World Trade Center bombing in 1993 and has killed more than 100 Israelis in suicide bombers can easily be detected using a spray developed at the Hebrew University of Jerusalem that literally catches terrorists red-handed. The detector spray was developed by Prof. Joseph Almog of the university's Casali Institute of Applied Chemistry, formerly an Israel Police lieutenant-commander and director of its Identification and Forensic Science Division. The spray is applied to cotton swabs that have been rubbed on the hands of a suspect or objects he carried, and, if they have had recent contact with the explosive urea nitrate, the chemical turns blood-red. Urea nitrate is a powerful explosive that can be prepared by amateurs in "backyard" facilities and used in improvised mines and explosive belts. The compound is a colorless crystalline substance that looks very much like sugar, which makes it difficult to detect. The development of a color test will therefore be a significant aid to forensic scientists. The initial findings of the Hebrew University project, which was supported by the US/Israel Bilateral Committee on Counter-Terrorism, were published two years ago, in the Journal of Forensic Sciences. Although instruments already exist to detect urea nitrate, they are much more sophisticated and expensive. Almog says his inexpensive and easy-to-use spray can detect tiny amounts of the improvised explosive on suspects, door handles, luggage and vehicles, making it easy to distinguish between innocent looking powders and urea nitrate. Almog believes the spray will join the standard arsenal of law enforcement agencies, security services and the military and at checkpoints at air and sea ports. He said that as well as enabling better understanding of the chemistry of urea nitrate, this discovery may play an important role in legal procedures. His team has conducted much groundbreaking research in past years, including the development of the chemical called FerroTrace, which turns purple when the user has recently held a weapon. Almog is the recipient of the 2005 Lucas Medal, the highest award of the American Academy of Forensic Sciences, "for outstanding achievements in forensic science."