From the Douay-Rheims:
Neither let there be found among you any one that shall expiate his son or daughter, making them to pass through the fire: or that consulteth soothsayers, or observeth dreams and omens, neither let there be any wizard,
Nor charmer, nor any one that consulteth pythonic spirits, or fortune tellers, or that seeketh the truth from the dead.
For the Lord abhorreth all these things (Deuteronomy 18:10-12)
From the RSV:
There shall not be found among you any one who burns his son or his daughter as an offering, any one who practices divination, a soothsayer, or an augur, or a sorcerer,
or a charmer, or a medium, or a wizard, or a necromancer.
For whoever does these things is an abomination to the LORD (Deuteronomy 18:10-12)
What the dead in heaven may or may not do is not our affair. We have no basis on which to say they can do this thing or that in heaven. We do know from scripture what they may do here - nothing. listening to you would be included in that as that would be interacting with the living here. So praying to the dead is worthless for gain and harmful to the soul as it is sin. Remember, Saul was put to death for seeking favors of the dead. And one wonders if Jesus taught us how to pray, and advised there is but one way to God, why so many seem so desperate to find another way that is disallowed.