I usually charge a retainer prior to working for a client. Usually, the retainer is refundable to the extent that it is not consumed for legal services. I put this retainer in my client trust account and write checks to my law firm for legal services once earned.

I've noticed that many attorneys that practice criminal law or other types of litigation often charge a non-refundable retainer. Its my understanding that the purpose is to deposit the entire retainer in the law office checking account to claim (or book) it as income when received because it is "non-refundable."

This makes sense.....however, does anyone have any thoughts as to the ethical considerations pertaining to non-refundable retainers?

See the link below for a discussion on the use of retainers in Minnesota.
http://www.courts.state.mn.us/lprb/91bbarts/bb1191.html

I think if you look at the State Bar Ethics guidelines, its at best boarderline ethical to take large non-refundable retainers. But, I also think it wholly defensible, whether criminal or civil work is being rendered to a client. As long as its disclosed up front, in the retainer agreement plainly and clearly, there is nothing wrong with it. If the disclosures are in place the client can make an informed decision or simply go somplace else. No ethical problems with it.