Originally Posted by Alyssa_Fox
after all dead people can't lie.


from https://www.dndbeyond.com/spells/speak-with-dead

Quote
Until the spell ends, you can ask the corpse up to five questions. The corpse knows only what it knew in life, including the Languages it knew. Answers are usually brief, cryptic, or repetitive, and the corpse is under no Compulsion to offer a truthful answer if you are Hostile to it or it recognizes you as an enemy.