Current_user in a model observer

I need to get the current_user id in my model observers:

Here is the code for current_user in the lib/authentication.rb file:

module Authentication
def self.included(controller)
controller.send :helper_method, :current_user, :logged_in?,
:has_role?, :is_admin?
end

def current_user
@current_user ||= User.find(session[:user_id]) if session[:user_id]
end

end

Here is the propsect_observer.rb file in models directory which needs
it:

class ProspectObserver < ActiveRecord::Observer

def after_update(prospect)
prospect.comments.create(:content => @comment_text, :admin_only =>
@admin_only,
:commenter_id => current_user.id) if @comment_text
end

end

current_user is not recognized here. I could include the module in the
observer, but that is bad(?). Any suggestion on a good alternative?

Thanks for your time.

Bharat

Forget it. Bad design. I am not pursuing this path anymore.