Bad cops (and I assume this can easily worm its way into the culture of a department/division/unit rather than being a strictly individual bias) have a long his

Bad cops (and I assume this can easily worm its way into the culture of a department/division/unit rather than being a strictly individual bias) have a long history of using just about any convenient lever within reach to apply more scrutiny to people who they already believe are guilty of something, regardless of whether the justification is supported by any objective facts or sound reasoning. Classic examples include planting evidence, "smell of marijuana", and "furtive movements", but there are countless other tactics. The "good" cops might be reluctant to push back on this pattern because they see value in having such tactics in their back pocket for extraordinary circumstances (cf. the various "is torture justified in a ticking-time-bomb scenario" debates and thought experiments, or just most seasons of 24).