Plum tree: branches that appear to do nothing

Wayside

I have a plum that has gotten a little crowded and tall.  So the fruit is too far to pick.  A gardener friend suggested I could chop the top of it, to try and tease it into a better more even canopy.  But some branches on the shadier side, are not in leaf at all.

My question is, whether these are dead, as they are not in leaf or bud or anything?

Or will they possibly come back to life given say some pruning elsewhere?

 Should I just cut them off and be done with it?

Photos are hard for this tree as it's a bit intermingled.

Obelixx

Pruning plum trees is a job to be done at the correct time of year to prevent disease and also to encourage fruiting spurs.  The best I can advise is that you go to the RHS website for info - 

https://www.rhs.org.uk/advice/profile?pid=339 

pansyface

If they are dead they will snap when you bend them. They will be brown inside.
If they are alive they will bend but not snap easily. They will not be brown inside.