We report an alleged case of sexual assault in which an anti-wrinkle cream could have been used as a lubricant. Three anorectal samples taken from the victim were given to us in an attempt to document the presence of remains of the cream involved. After examining the composition of the cream, octocrylene (OCT) was selected as the most relevant marker for this analysis. An ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed for identification of OCT. Anorectal samples were diluted with methanol and injected onto an Acquity BEH C18 column using a gradient mode with 0.1% formic acid/acetonitrile as the mobile phase. Data were acquired using positive electrospray ionization and multiple reaction monitoring. Three transitions were selected for OCT (m/z 362.2>250.0, m/z 362.2>232.0 and m/z 362.2>204.0). The analysis of the cream seized at the offender's home confirmed the presence of OCT as an ingredient, and the analysis of extracts from the anorectal samples also allowed the formal identification of OCT. These results strongly suggest that a cosmetic containing octocrylene as an ingredient has in fact been applied to the anus of the alleged victim.