Conventional ways people (and law enforcement) use to spot a liar is pseudoscience. Research studies have found that markers like fidgeting, looking away, and emotional response are not science-based and no better than guessing. This is problematic in the justice system and other law enforcement like the TSA because they are convicting people based on appearance of guilt that is baseless.
Alternatives that are found to be effective and science-based include withholding evidence to catch contradictions and sketching interviews which aids in recall (liars are less detailed).
See also:
- This is an example of structural racism e.g. cultural differences about eye contact will result in racial profiling
- Interrogators may believe spotting liars is tacit knowledge, but that was also found to be incorrect