document, document,...
as a retired lawyer , EMT b and former assistant DA, I can tell you that the more accurate documentation you have , the better off you are when you are called to testify about something 5 years after it happened. if what was written is unclear to the supervisor reading your report, it is perfectly legal, and 'ethical' for him/her to ask you to make a further (truthful) explanation. (and perfectly legal to fire you if you refuse to do so...) if some patient decides to sue everyone on the transport for assault and battery, you may be glad that you were made to add documentation clearly explaining why the pt was 'unable to sign..'
... and here in my state a CNA, like my sister, is a certified nurse-anesthetist, who not only has an RN 4 year college degree but also a year more of nursing education and advanced certification and training in anesthesia administration .. which makes a CNA a higher level of training than most emt b' s or paramedics..