Ultimately, you're not going to completely keep out all the people banned all the time. Duty to treat exists for a reason: in an emergency, it's better for society if people get emergency treatment and sometimes the other bits (e.g. money) don't work out.

However, most people who consume emergency services, don't do so unconscious. Hospitals, EMS, etc. want to get paid, so you're going to be asked for an ID sooner than later.

Some people might not want to give ID, or just not have it on them. I don't know what hospitals do in this case currently, but it doesn't seem like a huge stretch to just make those people give fingerprints to continue treatment.

This[1] claims that 4 finger IDs from fingerprints are 99.9% accurate, which isn't perfect, but it's pretty good.

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1. https://www.nist.gov/news-events/news/2004/07/nist-study-sho...