I mean the Wikipedia article on it basically says as much: https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis https://en.wikipedia.org/wiki/Bloodstain_pa

I mean the Wikipedia article on it basically says as much: https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis https://en.wikipedia.org/wiki/Bloodstain_pattern_analysis > The validity of bloodstain pattern analysis has been questioned since the 1990s, and more recent studies cast significant doubt on its accuracy. A comprehensive 2009 National Academy of Sciences report concluded that "the uncertainties associated with bloodstain pattern analysis are enormous" and that purported bloodstain pattern experts' opinions are "more subjective than scientific." The report highlighted several incidents of blood spatter analysts overstating their qualifications and questioned the reliability of their methods. In 2021, the largest-to-date study on the accuracy of BPA was published, with results "show[ing] that [BPA conclusions] were often erroneous and often contradicted other analysts." That's not the same as saying it could _never_ be done properly, but the analysis being done right now is not that, even though it's presented in courts as expert opinion with high certainty.