Dodging an invisible person -- where are the rules? If a person doesn't know an attack is coming, then they can't try to dodge it, right? I see the -6 penalty for a character trying to shoot at an invisible person, but what about melee attacks and (more specifically) dodging those attacks?

If the defender is unaware of an incoming attacking, then no defense is possible. Treat the attack as a success test instead. SR4A p159

The attacker gains the advantage of the surprise and ambush rules. The defender cannot react or act against the attacker. This works for the first round.

For subsequent rounds I would continue to use the surprise rules as indicated by Surprise Within Combat. This makes it more likely the defender will get to act in some way. It introduces the level of randomness and resolution that sometimes they can get lucky and dodge the incoming attack, and sometimes they can't Make note of the perception test in the surprise rules.

In principle you can consider all attacks from an Invisible source as surprises, and go from there.

edit: Or you can do what DWC said and use the Defender Unaware of Attack. Though that one says it does not apply once the character is engaged in combat. You can also look at Superior positions on p. 158 which in turn references the surprise rules on p. 165

The person is invisible, but not silent, so apply a -6 modifier for all defense tests?

well, my response would be to turn on my active sensors (radar/ultrasound) and then proceed to beat mr not-so-invisible down. and hopefully the team hacker can use data from my PAN to give the rest of the team some idea of what we are looking at.

its really difficult to stay fully invisible against someone with enough mods.

This works for the first combat pass. After that, you are aware of your opponent, you just can't see him.
Mechanically this should be equivalent to melee combat in complete darkness, hence you would get the -6 modifier to defend and attack.

That said, I think I would allow some kind of Infiltration roll (e.g. disengage from melee, sneak up from behind again) from the invisible attacker to regain the surprise.

-CJ

Actually, it's really easy if the magician uses the rules for making custom spells. A full-on "Cloaking Field" spell that applies against all senses would only be +1 DV up from Improved Invisibility. Not that I think it's balanced, but it is RAW.

Yes, that's why any person who's typically invisible should start picking up the infiltration skill and rolling that every round that they're invisible. Even if they see through the spell, you're still "hiding".

If you're invisible and ambushing someone and fail to incapacitate them on your opening attack, you probably should have walked past them rather than engage. Just sayin'.

Kill it or ignore it, everything else is more trouble then it's worth.

Indeed... Very Difficult...

Keep ther Faith

I'd run it like this;

- You get a chance to sneak up on the people who can't see you (provided they have no ultrasound, radar etcetera!). They use the -6 visibility modifier to their Intuition+Perception test to detect you, because people do tend to rely a lot on their eyes.
- Should you succeed in sneaking up on people, your first attack is a Surprise; the enemy gets no chance to evade etc.
- From then on, they're just defending at -6 due to being unable to see you.

- You could take a Complex Action to disentangle yourself from the melee.
- When you're disentangled, you're hard to pinpoint; you could move in for another sneaky attack. Again people must succeed at Perception to know you're coming, but at least this time they get the +3 for Actively Searching. If you still succeed at sneaking, you can attack people again without them having a chance to evade.

This means that you can attack at a slower pace (extract, then sneak in again) in order to leverage your invisibility more fully.

It all goes out of the window if the enemy has one guy with Ultrasound and they have a TacNet; he can share "you" with his whole team, and they're no longer at risk of surprise attacks.

Yeah, I'm a fan of stacking Invisibility with a Spirits Concealment power. Double my chances for remaining hidden, and the Concealment will cover me on the Astral as well.

Bull

Um...
SR4A p.293

Type: Powers may be either mana (M) or physical (P), just like spells (see p.203). Mana powers do not affect non-living targets, whereas physical powers cannot be used in astral space or affect astral forms.

SR4A p.293
Concealment
Type: P

I like Infiltration, because it WILL work in meat world or in astral. Also is what I consider a core skill for a shadowrunner, especially stacked with Concealment+Invisibilty. Works well against non-visual forms of perception as well.

Umm...

P.293 SR4A

The wording of Concealment and Dual Natured creatures leaves it a bit open to interpretation. Caine Hazen, our GM, decided that for the purposes of something that becomes dual natured, such as a mage that is sustaining a Spell, or active Foci, that these are covered by the Power. I imagine that they wouldn't work if I was Astrally Projecting though, since it's a Physical power. Bascially, it protects me from looking like a Christmas tree astrally while we're sneaking in, and hives the mage a way to use stealth without actually having the skill.

Bull

Ah, I missed that last sentence under Concealment on p.293. DOH! That changes everything! Hm, it is kind of vague on what exactly it works on. I like Caine Hazen's interpretation, it makes sense.

Hasn't come up in my game, as the NPCs so far have not had a reason for hiding from the players, and frankly my players aren't that bright...

I may have to edumacate my players a little on the finer points of Concealment. I try to teach a little something with every session, since most of them haven't played Shadowrun at all before.

Thanks, Bull (and Caine Hazen)! I learned something new (that I should have noticed before).