[X] My Assistant

[Samaels Ghost]

Black Ops agents using Fake SINs would be fine to check into. If queries into the authenticity of said SINs were sent back to the SINs repoisitory such queries would be redirected to special clerks who are there to cover for the Black Ops agents.

For that matter if the UCAS uses a Black Ops agent they can create Fake SINs better than any shadowrunner could get his hands on and be sure that either the data provided is flawless or that anyone checking into a flase-positive during , let's say, a border crossing would be covered by the SIN agency.

"WHat's that? Joe Spysworth's info doesn't check out? What exactly is the problem? Retina scan, eh? DNA too? Well let me talk to my superior, I'll call you right back."
----1 hour and a little data propagation later----
"Hi, this is Jill DataClerk from the UCAS SIN registry. Yes, i've double checked his information and it seems as if you must be mistaken. Please double check. Yes I'll hold.............It's correct now? Isn't that just hinky? Oh well, Deus and all that, you understand. Have a nice day and don't hesitate to call back if you have any further difficulties."

It's the government, please.

[Drraagh]

[ornot]

@drraagh ooh! ooh! I know this one!
If you try to give someone a blood transfusion and it's not in the same blood group as them then bad stuff happens, and they frequently die. You've heard of blood groups A, B, AB and O right? Someone with the rare blood group AB can accept blood from all the other groups, someone with the (more common) bloodgroup O can donate blood to all the groups, A and B are restricted to their own bloodgroup and O. Then there are a bunch of other blood factors like the rhesus factor which complicate matters. But the important antigens are A and B (O is just an absence of A and B).

Thing is, these antigens are on your red blood cells, which are quite special since they have no DNA. Not having a nucleus leaves more room for haemaglobin for oxygen transport. You need white blood cells (also known as Leukocytes) to obtain a DNA fingerprint. So unless you collect some foreign white blood cells in your blood sample for DNA profiling you'll get the original host DNA profile. If a significant number of white blood cells was introduced you're quite likely to find a chimera, that is a profile made up from both DNAs. (As an interesting aside chimeras are more common than you would think, with some people having quite different DNA fingerprints from tissue to tissue due to alterations in foetal DNA or even the fusing of seperately fertilised eggs and such like).

When you change someones bone marrow you no longer need to worry about blood group, since you'll be changing all their red blood cells anyway. You do have to worry about MHC receptors, however. The Major Histocompatability Complex (MHC you see. Clever huh?) is found on all your cells (except red blood cells) and is the means by which white blood cells recognise self from non-self. The MHC will also express samples of proteins made within the cell. If the white blood cells fail to recognise the protein it must be foreign, suggesting that there is a virus, bacterium or similar within the cell. I probably haven't made myself very clear, but the gist is this: To receive a successful bone marrow transplant you need to share the MHC with the donor. For this degree of similarity your genetic code needs to be pretty similar, and since a DNA fingerprint doesn't match up your entire genome, just certain variable loci, you'll probably wind up with the same genetic fingerprint.

In response to the comment about ritual magic, I'd point you toward the RAW which states that to cast ritual magic you need a spotter watching the target. If someone seeking you out wants to cast ritual magic on you they need to find you first. As for material links, I think they took that out of SR4.

[Samaels Ghost]

Okay, while there is a lot of info here I don't feel like my question has been answered fully.
ES Sparky said it best when he asked:

[Phobos]

Half (three-quarters) the problem is that any Country/Corp will not usually share the data stored in it's SIN registry with other Countires/Corps. Second, the only central SIN Registry is operated by the Corporate Court (who will not run any 'unncessary' checks as a matter of policy). This usually prevents you from finding out if someone in your Country/Corp's registry is also registered elsewhere. So, if you're smart and your different SINs have different nationalities (e.g. UCAS, CalFree, SSC, CAS for someone living in Seattle) there's little risk ... well, about none ... that your other SINs will be compromised if one is. That would only happen if two or more parties cooperated in hunting you ("who did you screw over to to warrent THAT ? Get away from me ... hey, I don't know you at all ... no clue who you are, really ... Phone Prank! Phone Prank! <click>").

If you have a number of different SINs with the same entity, you usually should take some precautions : different sets of fake fingerprints and retina modifications (cyber or contact lenses), masks (yeah, oldfashioned disguise), voice modulation ... enough effort that there really IS a difference in the data. If not, well, yes, then you could fall prey to a random check.

Now, how much effort would such a check be ?
Let's take a small-sized country or AAA Corp with 10 million entries.
It would take 50,000,005,000,000 comparisons to complete it.
So a computer rated in Tera FLOPS (pretty much any mainframe in 2070) with enough running memory (pretty much any mainframe in 2070) could do the taks in a few seconds.
Even checking the registry of a highly populated country would not take more than a day ... probably about an hour.

So, yes, any GM could use this to enforce the players take precautions. Not necessarily a good idea for a newbie group (so it's not in Core Rules), but a good idea to prevent an experienced one from getting lazy.
In 2050, processing power and memory were still an issue, but since the 60s ... yeah, 'running out of excuses :D
No, seriously, yes, you can make it an issue, but make sure your players know it and can prepare for it - or you can simply assume that they take all the necessary precautions and let it slip.