IIRC the AFA only required for an officer to charge someone with being drunk. This was years before drink-driving or breathalysers. Clearly there were margins for error and probably erring on the too lenient rather than the too strict.
"He was unsteady on his feet, his breath smelled of alcohol and his speech was slurred. Sir, he was drunk"
In the ARA (in the 1960s), the officer or NCO had to decide on the basis of the suspect's actions and appearance, whether someone should be charged with drunkenness. He would later be required to present this as evidence, usually in the form quoted above. He was specifically prohibited from applying a test or asking the 'suspect' to perform any action to determine his sobriety.