The forensic comparative analysis of cling films often lacks the capability to discriminate samples to the level required for court purposes. Isotope ratio mass spectrometry (IRMS) can be used in addition to the traditional forensic analysis to add further discrimination to soft polymers such as cling films. Seventy one cling films purchased from around Australia and three sent from overseas were used to determine the variability of isotopic compositions in polyethylene cling films from Australia and to create a background database, useful for identifying the strength of comparisons. These were all analysed using Fourier Transform Infrared (FTIR) and IRMS and the results showed that FTIR analysis could discriminate 73% whilst IRMS can discriminate 95% of cling films. This study demonstrates how IRMS can be applied to the differentiation and sourcing of cling films if associated with a crime in Australia.