Spawn protection is setup to immediately slay persons who fire at team mates within a configurable timelimit after the round starts.
The spawn time limit is from when players can move after buying weapons.
If a player has not spawn attacked on the map. The first punishment will be that they are slayed instantly.
The second time they spawn attack, the player will be slayed and miss the next round.
The third time a player spawn attacks, the player will be slayed and miss the next two rounds.
As you can see the punishment grows the more a player spawn attacks.
Changing team, sitting out round or leaving and re-joining the server will not make any difference to the punishments.