I believe that, even better and, parenthetically, more difficult to forge than a retinal scan would be an Iris Scan. Now, such a scan would have to be such that it ensured that the iris being scanned was, in fact, an alive iris, hence the bloodpressure sacn. This would pretty well exclude contact lenses, however, not entirely. That is why thre would also have to be an accompanying colorimetric multi-level scan, to ascertain that there were no background layers of non-matching color.
SO, you say, why not fingerprints? Too easy to falsify with a fingeerprinted finger 'condon,' which, alas would pass the bloodpressure scan. Hence it would not be able to discern between a 'real' fingerpring and a ;'forged' one.
Retinal scanning is satisfactory for the noncognoscenti, but anyone with decent technology can circumvent this process. I will not go into how - find out for yourself.
Voice analysis would have been great - until about 1970. Digital voice altering algorithms are so advanced today that you can forget this before you even think about it.