Did anyone have access to the original publication and can tell me, if they explain how they determined it being the first study and what other liquids have been used before in studies? The Guardian article only says "Manufacturers have traditionally used saline or water", but that does not tell you much, as these are not scientists with independent studies and manufacturers usually do not publish their full internal testing methods.
I only have access to its abstract and curiously it does not mention it being the first published study with actual blood, so the authors themselves did not find it very noteworthy.
I can easily imagine, that a published, standardized, reproducible (model) menstrual fluid for such an analysis does not exist yet, but I am not that involved in medical publishing. If this is the case, that would be really infuriating. It might exist as some vendors sell artificial menstrual fluid.
Even that is a very American way of thinking. The number of gun shot wounds a police officer sees in the US is way higher than in comparable European countries.
I could not find exact data for wounds, but if you take gun fatalities as placeholder (I am sure they are connected) here:
https://ourworldindata.org/grapher/homicide-rates-from-firearms?tab=chart&country=AUS~USA~DEU~CAN~FRA~ESP~ITA~JPN
You can see that precovid (2019) in the US there were 63x more gun fatalities than in Germany per person. In an average 1 million person city the police in the US has to deal with about 32 gun fatalities. In Germany that city has 1 every other year, in Australia it is 1-2 every year.
While the fictional US police department has every two weeks one or more fatality, the fictional German and Australian see it once a year.
So the frequency of it occuring and it being written about is way higher in the US than in comparable countries.
(Of course the comparing the amount of firearm fatalities between countries is not an exact replacement for gun shot wounds, but it should be close)