With algorithms, I think it can be done... but given how subtle the negative effects can be, the process must be stringent and err on the side of caution. In other words, any algorithm should be assumed to be biased until proven otherwise, and with a relatively high bar at that. There should be clear technical standards for what constitutes a valid proof. The testing process should be reproducible by third parties. And there should be a straightforward way to challenge either the process itself, or its results in any particular case.

In practice, given how low our bar for law enforcement accountability is today in other cases - including those where people die or are badly hurt - I'd say that we need to fix those issues first before talking about face recognition and its regulation in this context. And until then, it should be off-limits, because the potential for abuse is so high.