Do the guards right after the jail cell count? The tutorial says to stealth kill or knock one out non-lethally? Literally the first minute of the game or so proper, he has his back turned. If so I'll need to look for a way not to kill them.

yeah you choke him and drag the body out of site
i did the prison without raising an alarm
and did not kill any one
really hard to play that way

Should be possible with a no detection, no incapacitate playthrough aswell. Sounds very hard though. I guess you have to pickpocket those keys then