The behavioural effects of alcohol and drug abuse may lead to arrest by the police. Individualswho abuse one substance may be at risk of developing multiple drug dependencies. Using the forensic records, data were collected on 50 successive subjects detained in police custodies across West Yorkshire, England who had gave history of alcohol addiction to a single practitioner. The degree of correlation between alcohol dependency and illicit drug usage was assessed by calculating the Spearman’s Rank coefficient. Thirty three subjects in this study did not use any illicit drugs. There was no correlation between alcohol dependency and concomitant drug abuse in this group. Spearman’s coefficient was statistically insignificant (p = 0.230). Kruskal’s Gamma, which is used for comparing ordinal data, also failed to show a significant link between the alcohol and drug group (p = 0.185). As the degree of alcohol dependency increased, co-use of other drugs decreased. Conversely as the use of stronger drugs increased, co-use with alcohol and other drugs increased. Alcohol dependency is a distinct disorder. Once alcoholism had set in, the use of other drugs falls. The forensic behavioural patterns linked alcohol with “violent disorder” and Class A drug abuse with “organised crime”. This study does not support the contention that most alcohol dependent individuals will also abuse illicit drugs.