Courts can order a PEth (phosphatidylethanol) blood test to detect recent alcohol consumption, and it is significantly more accurate than the “PEF test” referenced in older discussions of this topic. PEth is a direct biomarker that forms in red blood cells only when alcohol is consumed, giving it a detection window of approximately two to four weeks, with a longer window for individuals who drink chronically or excessively. Because it measures actual alcohol metabolites rather than indirect organ-damage markers, PEth has a sensitivity and accuracy rate far exceeding traditional blood panels, making it a highly reliable tool in custody and modification proceedings. This means acting quickly after an incident remains critical, courts can only order testing that captures the relevant timeframe, so delays in seeking legal intervention can eliminate the evidentiary window entirely.