On our last run we broke into the safety concominium of a russian gang leader (Vory). We had to extract his personal security hacker and there was no other possibility than bombing his roof away and shooting most of his sec. guards. (I would have preferred to float his rooms with neurostun but my team collegues wanted to do it oldschool). We managed to finish this thing in about 9 combat rounds and left before Lone Star arrived. Unfortunately i got informed afterwards that some mages managed to get some blood samples i have left and that they assensed and recognized my astral signature (7P damage from a shotgut and at least 5 level 5 spirits that caused some trouble under his grunts, plus a variety of high level spells i casted during the run). But the first question i have is, if it is realistic that they had a chance to get a mage there in time to assense before my signature faded and if the blood samples could be used even if it took them at least 10minutes to get in reach of them. Do you think the star has such tactics that include magical support within this time?

Well astral signatures last Force hours and mage could use projecting to get there.
"Running" while projecting is 5 km per Combat Turn. Even "Walking" while projecting is 100m per Combat Turn.

So yeah, they have plenty of time.

Of course, you are right, but do you think that it is a standard procedure that an astral investigator is commanded to do so as long as it is not absolutely sure if he is needed?

This is a lesson.

Get Sterilize.

Also, become good buddies with someone who has been Astrally Hazed. Ritual spells will more or less just fizzle if you're buddy-buddy with the guy (Force = Force - 4!)

Who is doing the investigating, Vory or LS?

LS magical resources are stretched pretty thin, so in most cases, no, however if it's a high profile case and/or has obvious signs of magic, then it's not unreasonable to get those resources on site within about 2-8 hours. (However, they're unlikely to attack you like that.)

Vory is going to investigate right away, with mages, the attack of a major leader. They would be on your butt ASAP. In fact, it's almost surprising that astral support didn't come in while you were in the process of busting in ('almost' because you were in and out in 9 rounds. Longer and they should have been there.)

Well..

* An astral signature lasts Force # of hours. Removing it takes Force # of Complex Actions of a mage with astral perception active. (SR4, p. 182-183). However, you can't track someone with an astral signature; you can only track someone through an active magical connection.
* A Material Link can be used as a magical connection for the purposes of astral tracking. (SM, p. 28-29) Bloodstains only last a couple of hours unless carefully preserved however, and using a material link destroys it.

So, if they get a wizard there within a few hours, they can collect the bloodstains, freeze them and then track you down, yeah. How to prevent this in the future?

* Use the Sterilize spell; it nullifies tissue samples.
* Make time to erase all your astral signatures.
* Get the Flux metamagic (SM p. 61) to disconnect from material links while they "cool down".
* Get the Flexible Signature metamagic (SR4, p. 189-190) to reduce how long your signatures last, or disguise them.
* Get the Cleansing metamagic (SM p. 55) to quickly wipe all the signatures from the place. (Magic+Counterspelling, threshold highest Force signature; but success removes all signatures in a single complex action)

Doesn't look all that easy huh?

Regarding the realistic part of your question . . you are playing a mage . .

Hrhrhr....yeah. So let´s say in-game-realistic.^^

It was an investigation by the Star. They also screwed up the whole Vory section in that house and some of the LS-mages remembered my signature. This was my main complain because i cannot imagine that this very special mage that once recognized and assensed my signature, was ordered to come by and check this very special case. Or is there a possibiliy to "tell" or "explain" somebody else how my signature/aura is looking like?

Besides that, we had an enemy-mage that attacked us during the run (he was one floor below our target) but i managed to take him out (actually he took himself out by attacking one of my spirits with a manabolt from the astral plane - his own drain let him fade)

Well, if LS ignores the Vory because they just don't notice.. that'd be unrealistic. If they ignore the Vory because they're bribed or scared, well, that's LS for you.

They could also try getting Genewipe from page 89 of Augmentation to reduce the length of time it takes for your material links to "go cold". Difficult to find, and pricy, but it's another option.

Or use C-Squared.

(After all, it's what the Boondock Saints would do.)

Very realistic, actually, assuming you've been operating regularly in this area. The rules explicitly say that a mage who witnesses an astral signature can recognize it forever more. Mages are very rare and expensive, so Lone Star doesn't keep a lot of them on hand. That means the Astral Forensics group is pretty small, and you're going to have the same group covering all suspected magical events in that given area. And all that means that you're probably more likely to not get investigated at all by Astral Forensics, than you are to get investigated by a different guy than who did it last time.

However, again, the fact that they used that to attack you is unrealistic. Since this happened after the crime, and they had no reason to suspect you were threatening anyone's life at that moment, their obligation is to try and subdue and arrest you for trial, not to kill you. Did you piss off any cops recently? Could be someone is trying to exact street justice on you.

So you blew the roof off a wealthy person's house, killed all or most of his security personnel and kidnapped someone? Yeah, I'd say a robust police response including forensic magicians is reasonable (to say the least).

To answer your question: if the forensic mage that assessed your signature previously were an initiate he could have the Flexible Signature metamagic (SR4A page 198), in which case he could reproduce your signature for all his mage buddies on the force...

Don't do high profile crimes in a high profile way. Sterilize isn't assured to get all the evidence if you are busy bleeding. It's LOS, which means if you can't see the sample...

And don't forget the Quicksilver Mana Sensitive Film Camera. The forensics team won't.