I would have your client get tested when not drinking at all, to see if he has alcohol levels then. If he should have some severe Candida infection in the GI tract, there may be a positive reading when not consuming alcohol.
The main way to have elevated alcohol may be from faulty liver metabolism (damage).
Also what is his definition of two beers? Huge volumes of beer in each glass or a large Colt 45? Colt 45 is 5%
Some of the Lyme symptoms list "intolerance to alcohol and increased hangovers" This is rather vague IMO.
But there are people who cannot metabolize alcohol at all and these folks have a genetic error in the enzymes that process alcohol in the body.
This is most common in people of Asian descent, but can occur in anyone:
Often these individuals become quite ill from alcohol and the metabolic byproducts it causes. So they tend to avoid alcohol therefore.
Here is a calculator for people with normal health:
80oz of Colt 45 in a 150lb person within one hour= .185
I think the calculator can help you figure out the truth that you seek. Hint...people always lie about alcohol consumption.
Ask any doctor that and they will tell you.
Take your client when sober Test them, and sit with them, and watch them drink 2 regular 12 oz beers (not Colt 45 or other malt lager) and then test again. That is the only way to get a true reading for legal purposes.