But police tape is there specifically in order to let people know: don’t cross this line. So, it would be his fault for crossing it without authority. It would be the fault of anyone who did, but especially unforgivable for a legal professional to have done it. Frankly, it’s outrageous behaviour.
PS: I get that you’re just positing what they might mount as a defence to this action. I’m just saying that it would be weak as hell since police tape is used specifically and only in order to indicate to people that they may not enter an area.
I.e., Not my fault you left your door open and I entered your home! Actually, yes it is. You aren’t allowed to enter certain areas and if you do, it is 100% your fault.