External foam and the post-mortem period in freshwater drowning; results from a retrospective study in Amsterdam, the Netherlands

•Determining the time of death of bodies recovered from water can be difficult.•The presence of external foam is an essential feature of bodies recoverd from water.•External foam is only present in bodies recovered from freshwater with a post-mortem interval of less than 24 h.•External foam is an additional indicator for estimating the time of death in freshwater drowning.•It is unexplained why external foam is not seen after 24 h.

IntroductionDetermining the time of death of bodies recovered from water can be difficult. A feature of drowning is the presence of external foam. This study describes the presence of external foam in relation to the post-mortem period.MethodThe study utilizes a database of death reports dated between January 2011 and July 2016. For bodies recovered from fresh water, the presence or absence of external foam was noted.ResultsIn this study, 112 death reports are included. Of these reports, 18 mentioned external foam, which account for 16.1% of the entire study population. In the population with a post-mortem period of less than 24 h, external foam was detected in 27.7% of cases. All 18 incidents with external foam had an estimated post-mortem period of less than 24 h.ConclusionIn our study, external foam was only present in freshwater drowning cases with a post-mortem period of less than 24 h. Based on this finding, the presence of external foam may be useful as an additional indicator when estimating the time of death in freshwater drowning.