How can I tell if my iPhone turns on without a screen

I have two iphone 5's without screens. One was given to me from my brother a while ago after he broke it. (now that I know how to replace screens and do other iphone repairs) I want to see if the problem residied in only needing a screen replacment or if the issue runs deeper.

Unfortantly he cant recall how it broke but by the exterior (broken screen/ rear camera) I beilive it was crushed or dropped. He said "idk i think the home button didnt work" maybe he meant power button but again im not sure.

As for the other phone also without a screen which was given to my boyfriend by a buddy of his from school who said he needed a screen replacment and my boyfriend offered to fix it but his friend only bought the glass and not the whole digitizer lcd assembly. Long story short his friend got a new phone while he was back home visiting family so we still have the phone.

I dont want to go buying new screens if the phones have issues beyond that.

Is there anyway I can tell if the phones work by charging them or connecting them to a pc with itunes? Both screens were black with no sign of life that im aware of. This was two years ago.