I'll have to be careful here...
In American English, "screw" is commonly used as a more mild substitute for the Queen Mother of AE profanities, f**k.
This can be seen in the following common AE phrases:
Stop screwing around with that. You'll break it.
If you screw up this meeting, we'll be fired.
My car is screwed up. Let's take yours.
If I give one more wrong answer, I'm screwed.
I would have to know the full context of the "falsify" sentence to tell if this word is being used according to custom.