The State Council is due to make the sensitive call on the case of Vincent Lambert, who has been a tetraplegic since a car crash in 2008, at 1400 GMT.
The question of whether he should be kept alive artificially has split his family, and comes at a time of intense debate in France over euthanasia as the high-profile trial of a doctor accused of poisoning seven terminally-ill patients takes place.
But his deeply religious Catholic parents, another brother and another sister oppose the decision and took the matter to court in Chalons-en-Champagne near Reims, which ruled against ending his life earlier this year.
The case was brought to the State Council on appeal, and Lambert's parents say they will take the matter to the European Court of Human Rights if the council decides to end their son's life.
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The move to take him off life support would be allowed in France, where passive euthanasia -- the act of withholding or withdrawing treatment that is necessary to maintain life -- was legalised in 2005.
"The food and hydration being provided to Vincent Lambert are having no other effect than to keep him artificially in his current state," Keller said.
The State Council usually follows its rapporteur's recommendations, although it is under no obligation to do so.
"I would like the rapporteur's conclusions to be followed by the State Council, that we let Vincent go peacefully, with dignity," his wife Rachel told Europe 1 radio today.
His mother, though, told BFMTV on Monday evening that her son was not a "vegetable."