I recently was voulentold to donate blood. One of the questions I was ask was something along the lines of have you ever been in jail for more than 72 hours. Several years ago, I used to sell plasma and recall the same question.
Why does this matter? Is it because the average male can only go without sex for 72 hours and they figure he must have been turned while in confinement? Trust me, I can go a lot longer than 72 hours. I am married after all. 
SSG Schwartz
Presumably because the longer you’re in a prison the longer you’re potentially exposed to people (and practices) with a high likelihood of having HIV infection, hepatitis B, and hepatitis C.
Not that I agree, but I suppose it’s also possible that they’re using jail time as a surrogate for high risk behaviors, i.e. they feel that a priori a criminal is more likely to have used IV drugs, practised high risk sex, etc.
let’s not forget the high risk of infection from jail house tats, also, in addition to the other mentioned high risk activities.
but, IANABC
I would think along those same lines, NoClueBoy and KarlGauss, but they already ask about IV drug usage and tattoos, so wouldn’t a better question be, “Have you ever kissed a felon?”
SSG Schwartz
If I had been in jail for 72 hours and hadn’t gotten any, I’d turn straight too.
My son was recently in jail for 22 days, and while there they tested him for TB, so perhaps that is a concern.
He also shared with me that while he was harassed in the shower for his lame tattoo, there was no sexual harassment or sexual activity of any kind that he witnessed or experienced. The jail he was confined to the longest was just a big room with twenty bunk beds around the perimeter…and some guys had to sleep on the floor rather than in bunks. So there was no privacy, and nowhere that he could have missed something going on. He says that reports of violence and sex are highly exaggerated, at least for a jail setting. Prison might be a whole 'nother thing.
How about a factual answer from the Red Cross themselves … the criteria appears under the heading “Hepatitis Exposure.”
Thanks for the response. I knew it couldn’t be sex, but couldn’t understand the reasoning.
SSG Schwartz
But how do you think they got that hepatitis? 
HBV, sure, but not HCV unless blood is involved, generally speaking.
Wait, you can’t get hepatitis C from sex?
While it’s theoretically possible, Hep C is considered to be blood borne, not sexually transmitted.
Cites:
http://hepatitis-central.com/hcv/hepatitis/notransmission.html
While the CDC tends to cite a 1-3% risk of sexual transmission, my mother and I have both looked at a lot of the research and can’t find documented cases of sexual transmission without other risk factors (such as drug use, transfusions, sex involving blood-blood contact, etc.). About 20% of cases are labeled “community acquired,” which means “we don’t know how you got it.” HCV can stay alive outside the body for a while and there is documentation of transmission in medical settings. A recent study of people with HCV and their sexual partners appeared to show some sexual transmission on first glance. However, the researchers typed the HCV of the now-infected partner and in at least the majority of cases, the strain was different from the previously-infected partner’s. This means it was not acquired sexually; I read it to mean that more people are using drugs and sharing drug paraphernalia than admit it to researchers.
Another point is that people have a tendancy to lie on questions like “have you ever had sex with another man” or “have you ever injected illegal drugs”, so it’s in the Red Cross’s interests to ask proxy questions people are less likely to lie about, as well.
So, the question still remains, why is it 72 hours, instead of one week, two days or some other date?
SSG Schwartz
I just wanted to let you know that I’ll be stealing that.
Spelling it differently, but stealing it nonetheless.
And risk a Court-Martial?
(“Voluntold” has been in use in the military for quite some time. I first heard it myself on a tech course in 1996)
I gotta add, that I think it is in the public domain by now, so it is yours.
SSG Schwartz
[WAG] Perhaps it’s because 72 hours is what you’d spend in a holding cell, and any more than that they’d transfer you to a regular cell that has all the blood borne pathogens? [WAG]
Although The Red Cross is an excellent and accurate source for information regarding donor deferral, it is actually the FDA in concordance with the AABB (American Association of Blood Banks), that has created and maintains the guidlines for the rules of collection as well as deferral of donors.
Honestly, I think it’s 72 hours just to establish a general amount of time. I’m looking at my AABB technical manual now from 2002 (not the newest edition), and the question asks “31. In the past 12 months, have you been to jail or prison?” No mention of 72 hours. I believe they may have feared people would auto-defer themselves even for merely having a mugshot taken. They recently reviewed the list in February and may have made the change then.