Okay, so technically you can
cook frozen chicken in a slow
cooker and it should
cook fine - however because the meat will stay at a low
temperature for so long (since its
cooking so slow in the
crock pot) it will be in the dangerous range for meat for a long time which can make it easier for bacteria.
And from what I can tell, slow
cookers /
crock pots come with various
temperature settings, including low, medium and high.