Nigel Hawkes, Health Editor of The Times, discusses the resignation of Dr Woo Suk Hwang, the South Korean scientist who stepped down earlier today after his stem cell research was found to be faked

Who is Dr Woo Suk Hwang?

Before the current controversy erupted over his work, Hwang was widely seen as the world's foremost pioneer of human therapeutic cloning. In February 2004, his team published the details of the first cloned human embryo, beating rivals in the US and the UK, and he appeared to have topped that achievement with his now disputed Science paper of May this year.

In that research, Hwang purported to have created 11 "lines" or colonies of embryonic stem (ES) cells, each one cloned from a real patient with diseases such as Parkinson's and diabetes. The achievement was widely acclaimed as critical to the future of this technology - these tailor-made ES cells would be genetically identical to the patient, and could be transplanted without fear of rejection to treat their conditions. The work also had important implications for research, as it would allow the production of stem cells that accurately model genetic diseases.

Why has he resigned?

A panel set up by Seoul National University has concluded that Hwang's Science paper was intentionally fabricated, and not an accidental error. The fabrication took the form of manipulating data and photographs of two cell lines to make it appear as though 11 had been cultivated. The veracity of the remaining two is now being investigated.

How serious is the fabrication?

Very serious indeed. In science, there is no sin greater than faking data. Hwang still insists that he had some genuine data, but few will now believe that unless the continuing investigation finds he is telling the truth.

Will this cast doubt over his other research? What about his cloned dog, Snuppy?

The general rule is that when a scientist has been found faking data, all his previous work is discounted. Honest mistakes and errors of interpretation can be forgiven, and are even part of the process of scientific advance. But science depends, more than any other human endeavour, on honesty. Faked results can derail an entire field of research until they are disproved, and waste a huge amount of time and money as others try to reproduce them.

How bad a setback is this for stem cell research as a whole?

Probably not too serious in scientific terms, because it has been quickly exposed. But it will provide a platform for critics of stem cell research to attack it, which could damage the support it gets in some countries. Ultimately, like all new therapies, it will be judged by the results it achieves. These, most sensible stem cell researchers believe, are still some way off.

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