Or just someone skilled enough to place fake dna in his body such that the person taking the sample is fooled into taking it from the fake dna.

Yes, this really happened - at least once that we know of: https://en.wikipedia.org/wiki/John_Schneeberger

Wow!

During his 1999 trial, Schneeberger revealed the method he used to foil the DNA tests. He implanted a 15 cm Penrose drain filled with another man's blood and anticoagulants in his arm. During tests, he tricked the laboratory technician into taking the blood sample from the place the tube was planted.

Or someone just being careful with his DNA at the crime he commits, that then places someone else's DNA that he wants to frame?

That would work in the sort of Hollywood movie where the government has everyone's DNA on file.

Then again, I guess we've seen that you literally cannot be too paranoid.

>That would work in the sort of Hollywood movie where the government has everyone's DNA on file.

You don't have to have "everyone's DNA on file". It's actually pretty trivial even for your neighbor or whoever to get your DNA.

As for the police falsifying evidence, there's a wikipedia-long history of cases, in Europe, Latin America, Asia, etc. Especially in politically charged times, like the sixties and seventies. Heck, something like half of Italy's government in the 70's have been proved in later Italian courts to be involved in such things.

> You don't have to have "everyone's DNA on file". It's actually pretty trivial even for your neighbor or whoever to get your DNA.

Sorry, I wasn't clear. I can dump a gallon of your blood and semen onto a dead guy in an alley, but how would the government trace that blood and semen back to you?

They don't have to necessarily trace it back to me, as long as they can't trace it back to you.

A, sure.

Well, as the culprit, you can always arrange some things or leave other stuff that also points to me.

Also, your main benefit is that the police will more easily believe that it wasn't you (since your DNA won't match).

How in the world did he get off with only 4 years in prison after "repeatedly" raping multiple people?

In Schneeberger's case, it seems that he was simply infusing a part of his body with another man's blood and then making sure that the lab tech drawing the blood sample drew it from the same place. Once they tested his hair and saliva, they had a positive match.

The case of Lydia Fairchild is particularly harrowing, she nearly lost her own kids because most of her DNA didn't match. http://en.wikipedia.org/wiki/Lydia_Fairchild

Chimeras are also apparently way more prevalent than we had previously realized.

http://www.nytimes.com/2013/09/17/science/dna-double-take.ht...

> But scientists are finding that it’s quite common for an individual to have multiple genomes. Some people, for example, have groups of cells with mutations that are not found in the rest of the body. Some have genomes that came from other people.

> Women can also gain genomes from their children. After a baby is born, it may leave some fetal cells behind in its mother’s body, where they can travel to different organs and be absorbed into those tissues. “It’s pretty likely that any woman who has been pregnant is a chimera,” Dr. Randolph said

Or even mosaic individuals (which is slightly different): http://en.wikipedia.org/wiki/Mosaicism

And false positives in case of stem cell transplantation (a treatment of leukemia). There was a case where they got a false positive because of that. They discovered that it was a false positive because the alleged culprit had an alibi: He was in prison.