The term Lie Detection is a misnomer, but Indicators of Stress from Direct Questioning, doesn’t have the same ring to it.
The key to successful detection starts with establishing a baseline of behaviors and vocal indicators.
Ask peripheral questions to get an indication of how the person normally behaves. Then ask direct questions and observe their behavior.
Don’t focus on any one isolated behavior, but rather look for repeated clusters of these behaviors. Use the same tone with all the questions throughout.
Once you identify their stress behavior signals, don’t tell them! Otherwise, you’ll have to go through the baseline process again.
I would encourage lots of practice using kids, and non-friends, rather than family or relationship partners. You’ll avoid more fights and hurt feelings that way.