My first thought was "Consultant" but since the poster is the USA and "consulting physician" is commonly used there, I thought the longer term would be better for an U.S. English translation.

The longer term is sometimes used the NHS (UK National Health Service) no less. Please Google "consulting physician" nhs site:uk.

In the UK, however, I would use "Consultant" but in EU translations, I would use "consulting physician" to avoid confusion with consultant, which can also be a general term applying to many professions.

(examples: Google "consulting physician" site:europa.eu)

I would go with the Finnish Medical Association glossary on this one. The term seems to be used for doctors working in an administrative capacity (for an ethics committee or KELA, for example) rather than in a clinical capacity, describing a role that is not quite the same as that of a consultant or a consulting physician in U.K. or U.S. usage.

This depends so much of the overall text.
All previous words that have been given as answers are good, one just needs to know the context.
Source term is btw asiantuntijalääkäri, with an umlaut in the last 'a' , too.