Go onto Techdirt ( here ) and check Tim Cushing's blog. His beat is the abuse and corruption of our justice system. The latest issue I recall was using drones to peek into fenced backyards, into windows and deep across property lines, all without a warrant or probable cause.

During the 2010s IMSI spoofers were being used but the Stingray corporation required precincts sign an NDE so parallel reconstruction (creating an alternative plausible path of investigation to lead to the same discovery of evidence) was the norm. Eventually defense lawyers learned to press the issue, as even FBI would drop cases before admitting they used IMSI catchers to spy on where a suspect's phone was.

One of my bigger beefs is the misuse of detection dogs, which have up to a ~90% false positive rate, called Probable Cause on Four Legs it's known that most departments prefer trick-pony dogs who just signal a lot, in contrast to dogs who can actually detect stuff.

Interestingly, there is a subset of the K9 sector who train and handle detection dogs (which are still legitimately used, say to detect explosives in long lines of luggage at airports), and thanks to the common use of dogs to force a search, the public has been losing confidence in them, and courts who believe dog searches are for real.

often relying on getting a warrant post hoc or lying to establish probable cause.

https://en.wikipedia.org/wiki/Parallel_construction

Here's a whole ass Wikipedia article on the very subject, because it's been so widespread for so long it has a fucking name.

https://en.wikipedia.org/wiki/Hemisphere_Project

Here's a Wikipedia article on the mass surveillance by the DEA, which is where the data used for parallel construction was sourced.

https://www.reuters.com/article/us-dea-sod-idUSBRE97409R20130805/

Here's a good example from the first Wikipedia article about how the Feds pass signals intelligence to local law enforcement so they can start cases and claim they found the initial evidence some other way than illegal mass surveillance.

For more history about attempts to install backdoors, see:

https://en.wikipedia.org/wiki/Clipper_chip