Forensic alcohol calculations in transgender individuals undergoing gender-affirming hormonal treatment

There are an increasing number of individuals undergoing gender-affirming hormonal treatment (GAHT) to treat gender dysphoria. Current forensic alcohol calculations require knowledge of the sex of the individual, but this may disadvantage trans people as research has demonstrated that there are physiological changes in individuals who are undergoing GAHT. Using previously published studies on total body water (TBW) in cis individuals, and the known changes in lean body mass and hematocrit in trans individuals, it is possible to estimate TBW in trans individuals and compare them to those cis equation estimations. When using these revised rubrics, we determined that for trans women the use of the cis male anthropometric TBW equation only gives a small underestimation of TBW (0.9%) compared to the underestimation of TBW using the cis female TBW equation (-17.7%). For trans men, the use of the cis female TBW equation gives the largest disadvantage, underestimating TBW by -10.8% compared to the cis male TBW equation, that overestimates TBW by 6.6%. For this reason, we recommend that if the sex at birth of an individual is not known or disclosed, any forensic alcohol calculations in a forensic alcohol reports are made assuming that the gender declared by the individual is their sex at birth. Further research to develop validated anthropometric TBW equations are urgently needed as to not disadvantage trans people when forensic alcohol calculations are carried out.