harry potter - Can you transfigure a human into an inanimate object?

One of the first spells students at Hogwarts are taught is how to transfigure an animal into a goblet.

In fact, Ron attempted to turn Scabbers (who turned out to be Peter Pettigrew in disguise) into a goblet and got half way there.

Is it possible (or at least a possibility supported by canon) to transfigure a human into an inanimate object? If so, why wouldn't Dumbledore transform Voldemort into a lovely end-table or footstool?

Answer

Yes.

One example is Horace Slughorn, who transfigures himself into a couch to try to hide himself from Dumbledore or visiting Death Eaters:

Dumbledore swooped, plunging the tip of his wand into the seat of the overstuffed armchair, which yelled, “Ouch!”

“Good evening, Horace,” said Dumbledore, straightening up again.

Harry’s jaw dropped. Where a split second before there had been an armchair, there now crouched an enormously fat, bald old man who was massaging his lower belly and squinting up at Dumbledore with an aggrieved and watery eye.

— Half-Blood Prince, chapter 4 (Horace Slughorn)

Note also that Slughorn seems to be able to untransfigure himself despite having no hand with which to use a wand, although we don’t know how.

Alternatively, a character is turned into a bone and buried:

“Dumbledore told me to go and look for my father. I went back to my father’s body. Watched the map. When everyone was gone, I Transfigured my father’s body. He became a bone… I buried it, while wearing the Invisibility Cloak, in the freshly dug earth in front of Hagrid’s cabin.”

— Goblet of Fire, chapter 35 (Veritaserum)

As for Voldemort, remember that he’s an incredibly skilled wizard. Dumbledore could try to turn him into a footstool, but that probably be very difficult and Voldemort would try to stop him. I don’t think there’s much canon support for transfiguration during duelling.