The big equalizer in mature justice systems is a strict set of laws that regulate and restrict the instances in which evidence can be gathered and used in a courtroom. I think it's inevitable that technology is created, but not inevitable that it will be abused, at least, to the level we fear. However, this is ONLY if those checks are put into place. It requires a critical legislature to write balanced laws, and a strong judiciary that can hold investigators to account and throw out illegal uses of this technology in cases where it's abused.