Dr Alan Esler is a well-known forensic botanist, known to many as the "Cannabis man" after his enormously precise, illustrated pamphlet on cannabis identification was plagiarised by a US Drug Enforcement Agency. After lecturing for many years at Massey University, he was appointed in 1969 as the DSIR Regional Botanist at the Mt Albert Research Centre, where he remained for over 20 years, the acknowledged expert on weed identification and forensic botany in the Auckland area. He holds the Police Crest, in recognition of his services to police. He has been described as a natural teacher with artistic instincts and contagious enthusiasm and has produced a great variety of popular illustrated pamphlets.