State rules re: Expert Witness competency's?

Hi all!

I'm trying to find out what my local state laws are regarding how many hours I am required to work in my
area of expertise, should I decide to work as an expert witness. Obviously EW work is not limited to my
home state, and these laws vary by state. I had read in one book where some states require you work 50-80% of your hours in the area you plan to testify. Is that 50% of an FTE, meaning 20/hrs a week? 80% = 30+ hours, plus whatever time it takes to research a case and testify?

Anyone know where to go to find what each state requires? I searched online quite a bit and can not find specific requirements.

Thanks!!