That sounds like a good plan. You seem to identified a market that's easier for a startup to penetrate, which will then give you a basis for expanding into more lucrative customer segments.

Based on this discussion, I'd suggest that you deemphasize public defenders, at least removing it from your tagline. I'm sure there were others who had a similar reaction to me. Instead, pitch your service as one for the entire legal system, and then discuss how public defenders will be your go-to-market strategy.