system
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human
[Star Wars] How (and why) Count Dooku left the Jedi order and became a Sith?
gpt
In canon, we don't have an exact timeline, but essentially he fell under Palpatine's influence either before or during the events of the Naboo Crisis. He used Qui-Gon's death as cover, claiming that the Jedi had failed in their roles as servants of the Republic.

In Legends, he likewise used Qui-Gon's death as an excuse to finally leave the order which he considered was growing corrupt and complacent, but it wasn't until later fell under Palpatine's influence and joined him, sometime in the first year or so after TPM.