Yeah, using the specific example you gave:

If the PCs know who Baron Joris Iselmere is, or have seen him before, just tell them that, no roll needed.

If the PCs think to check the back of his neck, mention the incision. If they state they check the entire body carefully for wounds, that can still count. If one of them has the Diagnostics proficiency, you can have them make a proficiency check instead (the description specifically states you can use it to determine how someone died).

Basically, make a judgment call based on their background and skills if they know something or not, or just answer specific questions. In later editions, a PC might roll a search or perception check to notice that pulling down the red book on the shelf causes a secret door to open, but in 2E the PC will have to actually physically try pulling the red book down to discover it.