"police in Canada posed as tea vendors to massively collect DNA from the Kurdish community at a cultural event. They identified a relative of the person they were looking for which led them to make an arrest."

Via https://kolektiva.social/@cedar/111767532746573971 (see thread for more details & other known examples)

The author's takeaways:

"it is almost impossible to know what lessons to take from a situation like this one. But here are some starting points:

1. Undercover operations are far more common in Canada than we might suspect

2. DNA analysis is increasingly routine

3. Collecting DNA is in a legal grey area (may not require a warrant) and police will go to great lengths to do so"

My 2 sats on the topic: I don't think this is limited to Canada, although I can't cite specific incidents to back that up.