Answer: If the plant did not leaf out this past spring or summer, then it is dead.
If something happened over the summer, if the twigs are dry and brown throughout all the interior and exterior layers of bark and wood, then they are dead. You can start at the tip of each branch and work your way upward toward the trunk, chcking as you go.
Drought stressed plants may defoliate earlier than normal. This does not mean they are dead, just stressed. If this is what happened, keep the soil evenly moist until the ground freezes and hope for the best next spring.
Deciduous plants will defoliate in autumn, this is normal. They should leaf out again next spring.
I hope this answers your question. If you are still not sure, you could perhaps consult with local professional nursery staff.
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