My understanding is:
Head hair strand testing for alcohol is an overview for 3 - 6 months and does not detect use on specific times / weeks, it can only be segmented for 3 or 6 month periods.
Drug testing in hair can be segmented more accurately.
Some tests such as nail tests can be used for longer windows but are less accurate and are not used in preference of a hair strand test.
PEth blood tests cover around a month and are considered accurate however in reality how people process PEth varies widely (half life).
I'm going through something similar myself, my barrister has advised me that there have been recent successful challenges in court regarding the accuracy of hair strand testing, and the labs themselves always say they should never be used in isolation. So there is a risk of a false-positive, so resist if you can, basically.
I did a pre-emptive PEth test which came out fine (social drinking) but of course my ex claimed this wasn't enough, I have a bit of a history and expect I may get a 3 or 6 months hair test ordered along with another PEth test, I have also offered to do a few PEth tests in future which is a very reasonable offer, in my case I don't think it's really about alcohol and that may well be the case for you too. If you don't have a history it will be difficult to order anything more than a 3 month hair test and a PEth test at the same time, and even then you could argue that a hair test is disproportionate because you don't have a history and there are no specific incidents your ex can point to as evidence of a problem. Good luck.
