Mohsen Klibi, technical director for Tunisia’s swimming team, recounts his experience as former coach of Oussama Mellouli, individual medley swimmer and 800m world champion in 2005.

I knew a doping case that shook the whole country. Oussama Mellouli was one of my athletes and he was at that time 800m freestyle world champion and silver winner in 400m. I personally followed this experience when the scandal was revealed in 2007. Mellouli tested positive for amphetamines at the US open in Indianapolis.

I know Mellouli very well and I was surprised when he tested positive. All through his brilliant career, he never tried to enhance his performance by cheating. He refused to analyse the test B as he told us he had just taken a pill containing amphetamines. It was some Adderall that a classmate gave to him so that he could hand in a university project on time before going to the US Open. This product is a nervous stimulator that helps one stay awake.

This story is now behind him. After an 18-month suspension, he can go back to competition. Today, he is on his way to Beijing.

Gérard Dine, doping specialist, describes the latest technologies to detect performance enhancers.

At the moment, I am in charge of biological testing for the French athletes who will go to Beijing. That means hair, urine and blood controls to define the ‘biological passport’ of each athletes. This system enables us to detect any abnormality due to drug use.

I think the severe measures and the 4,500 tests programmed during the Games will certainly limit the use of performance enhancers, but they won’t make these Olympics clean. Especially when new ‘high-tech’ substances are now appearing on the market.

There are still some undetectable doping techniques. Following a targeted cell therapy helps enhance the human cells of an athlete who uses human growth hormones.

The experience of a German journalist who fooled an American swimming coach in China reveals the extent of the situation. A Chinese doctor proposed a treatment based on stem cells, what we call ‘genetic doping’.

I find it OK that new cases of doping are being uncovered in the run-up to the Games. It's the result of modern advanced technology that goes beyond the basic urine test, which has proved relatively imprecise. It confirms that the majority of tests should be conducted long before competitions.

I don’t think doping scandals like in Athens or Sydney will occur. But these Games will reveal new kinds of performance enhancers like biological doping that will definitely be publicised shortly.