I'm not proficient at American Sign Language (only conversational), and I know nothing of South African sign language, but it was TOTALLY easy to tell he was a faker. You know how I know? Three reasons.
He had a blank face.
In sign language (not that Signing Exact English stuff), the grammar structure is often in the face, as the facial expression is roughly like vocal intonation. A blank face is the rough equivalent to a monotone with missing connectors. of missing connectors in a sentence. In ASL, raising both eyebrows indicates the subject before you continue on to talk about it.
Here's two sentences:
With facial expressions:
(raised eyebrows) The book? (assured face, some nodding) It's on the table over (pointing) there, in the far corner (squinting while opening lips with teeth closed indicates how far it is, depending on how exaggerated the facial expression is).
Without facial expressions:
Book on table corner.
HUUUUGE difference. You see? The guy's face was mostly flat. There's a difference between the subdued demeanor that some interpreters have and the guy's flat face. And speaking of subdued, I really appreciate interpreters who let themselves loose with facial grammar. Like this gal, Lydia Callis, who interpreted during the Hurricane Sandy official announcements.
I <3 her so much. She's amazing.
His "vocabulary" was extremely limited, and had no finger-spelling.
When I tried to use my ASL knowledge to glean meaning from his signs, he was like the sign version of doge.
THINK ALL. HEART OUT. EACH TEMPERATURE. GATHER ALL. EAT SOUP. THANK YOU. ANNOY YOU ALL. LIQUOR. AIRPLANE SEE YOU. PICK NOSE.
He often used the pointer finger and flat hands, things that most hearing people recognize and remember when trying to repeat the sign to someone else later. And he kept repeating the same signs. It's like people speaking fake German. They repeat the same syllables they remember, except in different orders.
And there's no way one can NOT use fingerspelling during any given interpreting assignment. Not every word has a respective sign, although you can make one up for the duration of the interpretation. For example, nobody would spell Ahmadinejad over and over again, right? Talk about tiring your hands out. They'd spell it once, and give him a sign abbreviation (like, a A handshape on the shoulder for example), and use that abbreviation every time he's named thereafter.
He had none of that.
He had almost no classifiers.
What are classifiers? They're handshapes that represent objects or things, and you can use them to share a lot of information without having to sign a whole bunch. Instead of signing something like, "The airplane landed on the front wheel, did a 180, and had a bumpy landing," you can use the airplane handshape and sign all of that by miming the plane landing, on its nose, turning around, and bumping around. All with one sign.
He had none of that.
Take another look at Lydia Callis' interpretations--I remember when she interpreted information about cars and storm surge, she used classifiers to describe the scene instead of signing it all out, because that's what you do in sign language.
Whether they hired a non-professional, or whether he somehow faked his way up there pretending to be official, the organizers failed horribly. Either they chose to hire this guy without checking any credentials/references, or they didn't hire anyone at all. Either way, deaf South Africans who were watching or in attendance missed out. Completely.
It's still common to forget about deaf people in large events like these, but hopefully officials will learn from South Africa's debacle and make extra sure that they are hiring good interpreters.