Can I fall prone as a Defence Option?
Yes, eventually, but you are not counted as being prone against that particular attack. As far as the attacker is concerned, you are simply performing a Dodge maneuver. If you survive the attack, you’ll end up prone. Come to think, if you don’t survive, you’ll probably end up prone, too… 🙂 Against any other attacks later in the Round, however, you will be treated as being a prone target. The same rule can be applied if you wish to crouch or kneel while Dodging.