Keep in mind that if the defender is unaware of the attack there's no defense test at all! (Snipers are deadly...)
...but if the target happen to be behind partial (or full) cover it will roll 2 (or 4) dice as a pool of its own. This pool also apply to inmate objects that normally are not allowed to take a defense test.
But yes. Snipers are really deadly.
Consider this:
Sniper with a dice pool that is close to 20 dice take a shot at a wall where he suspect that his target might be behind but he doesn't have visual confirmation, in a blistering snow storm and in total darkness while located close to 1500 meters away... and not using a scope.
- Target unaware but roll 4 dice as a pool of its own
- Attacker take a -10 environmental modifier
- Barrier rules apply (as long as modified DV is higher than armor of the barrier then the barrier take 1 box of damage while the rest hit the unaware target behind the barrier).
Now you say "wait a minute!".
"In order to take the Blind Fire modifier he must have some idea of where the target is located, right?". Wrong.
Pay attention. This is the part where it get really interesting
Blind fire seem to only be applied when you have really no freekin idea at all where your target is located... as soon as you get
any indication on where your target is you are no longer firing blind. Even the slightest indication seem to be enough.
For example:
It make total sense that you cannot use your big pool of dice to attack an invisible target if you can't sense him in any way (it will be totally random if you hit or not... use supressive fire and other AoE attacks, right?) and it make total sense that if you hear an invisible target... then you have an idea of roughly where the target is but you still can't see him so you take the blind fire modifier and try to hit him. Right`?
-Wrong!
Crunch wise you take the blind fire if you can't smell him or in any other way sense where he is. When you have NO idea where the invisible target is. If you have a rough idea where your target is (because you friggin smell his deodorant or whatever) then you don't take a negative modifier at all. This is RAW.
It make total sense that you cannot use your big pool of dice to attack a target behind a wall if you have no idea where behind the wall your target is located and it make sense that if you have a rough idea where behind the wall your target is located because you have a drone to spot for you then you take the blind fire modifier to try to him.
- Wrong!
Crunch wise you take the blind fire if your target is 100% hidden from you. If you can see even 1% of him then you get a rough idea where behind the wall your target is located and you no longer use blind fire. In fact you no longer take negative dice modifier at all (but the unaware target get 4 dice to oppose you which i guess can count as a negative dice pool modifier of sorts). If you have a drone behind the wall to show you where the target is then you are not totally unaware where your target is located and you should no longer fire completely blind.
SR5 p. 178 Blind Fire
Whether due to darkness or cover, if the shooter doesn’t know where the target is, they apply the Blind Fire modifier. This modifier is the same as the Total Darkness modifier and as such is not cumulative with it, but if strong winds or extreme range are also involved an additional -4 penalty can be applied. Some additional rules apply if the attacker is shooting through cover (see Shooting Through Target Barriers, p. 197).(If you don't know where the target is at all you take this modifier)
SR5 p. 188 Defending in Combat
Note that even stationary or inanimate targets may have a defense dice pool if they have Partial or Good cover.(stationary or inanimate targets behind more than 25% but less than 50% cover get 2 defense dice as a pool of its own and 4 dice if behind more than 50% cover)
SR5 p. 189 Defender unaware of attack
If the defender is unaware of an incoming attack (he does not see the attacker, the attacker is behind him, or he is surprised), then no defense is possible. Treat the attack as a Success Test instead. This does not apply to defenders who are already engaged in combat (see Character Has Superior Position, p. 187). If the defender is behind cover, the defense dice pool is determined by the cover, according to the Defense Modifiers table.(Unaware Target behind more than 25% but less than 50% cover with or without taking a Take Cover action get 2 defense dice as a pool of its own and 4 dice if behind more than 50% cover)
SR5 p. 190 Defender/Target has Good Cover
If the Defender uses a Take Cover action to get behind something where more than fifty percent of the defender’s body is obscured by intervening terrain or cover, he gains a +4 dice pool modifier to his Defense roll against any attack. This modifier can also apply to prone targets that are at least twenty meters away from their attackers. This modifier is applicable to both Ranged Combat and Spellcasting.
Note that this modifier does not negate the Blind Fire modifier the attacker suffers. Both the modifiers to the attacker and to the defender would apply when firing at a target that is totally concealed (one hundred percent behind cover).(If the target is covered by less than 100% then then blind fire modifier does not apply).
SR5 p. 197 Shooting through barriers
If the defender is completely hidden behind the barrier, the attacker suffers a –6 Blind Fire dice pool modifier for not being able to see his intended target, but the hidden defender is considered unaware of the attack. If the barrier between the attacker and defender is transparent, like bullet resistant glass, there is no cover or obstruction to sight, but the attack must penetrate the barrier to reach the defender (see Penetration Weapons, p. 198).(If you don't see the target at all, then you take the blind fire modifier)
SR5 p. 198 Shooting through a Barrier example
Wombat is hunkered down behind a concrete barrier reloading his Ares Light Fire 70. An Ares security goon makes his best guess where Wombat is and takes a shot with his Defiance T-250. With the Blind Fire penalty, he only has 4 dice but scores 2 hits. Since Wombat is behind the cover, the barrier takes the hit first. Base damage is 9P, modified by the 2 hits to 11P. This is far less than the Armor rating of the concrete, which is 20, so the shot stops dead.
When Wombat moves behind a security door (Armor 12) he stops for a quick breather. The goon takes a shot and scores 3 hits this time (lucky goon). The modified DV of the attack is 12P, equal to the Armor of 12, so the shot punches through. The door takes 1 box of damage, and 11P passes through to hit Wombat.(the guard don't know where behind the concrete barrier or the security door wombat is so he take a -6 blind fire penalty and just fire away)
SR5 p. 291 Invisibility
The subject is completely tangible and detectable by the other senses (hearing, smell, touch, and even taste, if it somehow comes to that). Her aura is still visible to astral perception.
Attacks against invisible targets suffer the Blind Fire modifier if the attacker is unable to see or otherwise sense the subject of the spell.(if you don't sense the target at all then you take the blind fire modifier and just fire away. If you do sense the target with one of your senses, such as hearing, then blind fire does not apply).