Gedankenexperiment

With all the poli­ti­cal and ethi­cal deba­tes about what allo­wed means for intel­li­gence should be or are, a ques­ti­on recent­ly pop­ped up in my mind: 

If a tech­no­lo­gy emer­ged that allo­wed humans to read other peo­p­les thoughts and memo­ries, under what cir­cum­s­tances should that be a legal way to find out about cri­mes that were or, even more inte­res­t­ing, are to be com­mit­ted? Not some­thing about pro­ba­bi­li­ties as in Mino­ri­ty Report, but actual­ly some­thing to read emo­ti­ons, memo­ries and thoughts? Whe­re are the bounds in this? Should it be legal in the con­text of inde­scri­ba­ble atro­ci­ties like 9/11? Mur­der? Rape? Theft? Only for cri­mi­nal inves­ti­ga­ti­ons, or also as a means for intel­li­gence befo­re the act? 

And to make it more inte­res­t­ing: What if the act of rea­ding were des­truc­ti­ve? If the sub­ject of the inves­ti­ga­ti­on does­n’t come out like he went in befo­re, but was eit­her irrepa­ra­b­ly dama­ged or even dead? Whe­re are the boun­da­ries then?