There is a mystery co-worker here whom we have nicknamed “The Dribbler”. This disgusting and rude individual’s lot in life is to pee all over the toilet seat and not wipe it up. We suspect on purpose, but maybe he has really bad aim and eyesight.
Anyways, no one has been able to catch this person in the act. Could a sample of the urine (there is never a shortage) provide any clues to who this person is?
I would assume some cells are presetn in urine, much like there is some cells from your mouth present in your spit. Anywhere there is friction your body gives up a few surface cells.
I would suggest a bathroom monitor for the data to be collected. After any person uses the restroom the toilets are thoroughly cleaned. Then when the mystery person strikes, you have a non-tainted urine sample, hopegully with some bladder or urethra cells.
But then, you might just be able to tell who is doing it by watching. 
There is DNA in urine. Every time you urinate, you slough off endothelial cells lining your bladder and urethra. There are enough cells in a typical urine sample to I.D. the culprit.
Incidentally, there is also DNA in feces 
You can actually buy kits to extract DNA from urine, feces, hair, blood, semen etc… I think Invitrogen/Life Technologies sells it to law enforcement and the FBI, although I will have to check on the exact manufacturer.
MM
Not only are there cells in urine, there are sperm cells in male urine. At any given time, there’s a few thousand sperm cells in the urethra. That’s why naive teenagers are routinely warned that pulling out before ejaculation is not effective birth control.
I forgot to add that DNA testing is not cheap, nor is it quick. Labs have backlogs, and police clients are ahead of you on the list. There are sneaky ways of obtaining samples from your suspect, I suppose, but you’d have a hard time coercing the fellow to voluntarily give you a sample.
Perhaps a better way to catch “The Dribbler” would be to set up a hidden toilet-cam. Not only will you catch him in the act, but you can make some money on the Internet!