Secret evidence in legal cases

Over the last century an exclusionary rule has been established in American law whereby evidence is typically deemed inadmissible if obtained as a result of violating the Constitution. ( The government tries to get around it. )

Here in the UK, ( the question of secret evidence has been tested in court. )

Last year I expressed disappointment that the Liberal Democrats don't make more of their civil liberties platform. After exiting the European Union I have little faith that the Conservatives will be at all restrained in further eroding human rights in the name of safety and order. ( The European Union may still constrain the UK. )

While I can see that there would be concern over encouraging unconstitutional surveillance by allowing its rotten fruits to then be substituted by palatable equivalents, I guess that I find most bothersome the idea of a defendant facing accusations founded upon uninspectable evidence, special advocates notwithstanding.