In this DWI prosecution, the Third Department determined the People’s expert was not qualified to offer testimony about “reverse extrapolation,” but that the theory itself was sound:

[We reject defendant’s generalized challenge to] the  theory  of  reverse extrapolation – the process by which an expert, taking into consideration, among other  things, an individual’s known  BAC at a particular point  in time, renders  an  opinion  as  to  the  individual’s BAC at an earlier point in time. Assuming the expert in question is qualified and a proper foundation has been laid for such opinion, reverse extrapolation testimony may be….  Here, however, the People failed to lay a proper factual foundation for [the expert’s] testimony and, therefore, defendant’s objection in this regard should have been sustained.  People v Menegan, 105337, 3rd Dept, 6-13-13