Very simple. This applies to all ill doings that you may want to achieve.

Before you do anything open up your steam profile and leave it open. Then open your friend tab click the down arrow next to your name and then have edit profile name open. You should have 3 different windows open. Your steam profile, Your friends tab and the little box that changes your name.

Now while in the server you can change your name ahead of time and it will change ingame once the round restarts.
So change your name at the beginning of the round and then go to your profile and click the down arrow and clear recent names (thanks to the recent update). Its very important that you clear your recent names because they will go to your profile and check for names of the accused team killer. But if you did everything right they will have no evidence of your wrong doings. Have fun and kill the ♥♥♥♥♥♥♥ d boys who close the doors on you.