DMong
colubrid connoisseur
it would also make it very easy to tell if a hybrid had snuck into ones collection so to speak. One may only have to look at the fact that you have all infertile males or most of your males are infertile for instance to suggest that there may be some hybrid goings on in their past.
That wouldn't tell anyone one way or another if any snake someone posessed had any hybrid influence, even though some hybrids might be sterile. There can be fertility problems with many "pure" line snakes just the same for any number of reasons. One would be temps being too high. That will kill sperm just as it does in humans or almost any other animal. There can be other unknown factors too. That scenario would be very inconclusive. A good microscope would be the best bet for finding out if there are high numbers of viable sperm, a low-count, ...or none at all in any male.
As far as females go, you would have to gently check as the snake crawled through your hand to feel for any egg follicles during ovulation. This is often known as the "string of pearls". The little soft lumps can be felt with the thumb or index finger with a slight bit of pressure applied to the belly as it moves across.
~Doug