Are police sketch artists asking the right questions, are they providing accurate sketches?

From the Daily Mail in England.
By Jane Fyer
This article shows that private investigators have their work cut out for them, when investigating sketch artists and witnesses.

"Jan Szymczuk, a very jolly man with lustrous grey hair, a splendid beard and a brown leather waistcoat, is huddled in the corner of a hotel bar in London with a sketch pad, a twitchy-looking witness and pictures of about a hundred chins. Jan, 50, is a highly-trained forensic artist who describes himself as 'the best in the country' and until his retirement in March had spent 30 years working as Senior Police Artist for New Scotland Yard helping witnesses to recall suspects in murders, rapes, robberies, kidnappings, you name it. But just how accurate are artists' sketches? And is a fleeting glance ever enough when it comes to identifying a nasty villain?
To test how helpful they really are, three people in the street were asked to watch like hawks as our pretend suspect - me - rushed past them looking furtive, and then describe exactly what they'd seen to Jan.
The results are rather startling. Although perhaps more alarming are the percentage marks, given by each witness to indicate how good a likeness they consider the picture to be.
And so, finally, back to our witnesses. After an hour with each - he'd usually have three to four hours per witness - he comes up with three sketches of our 'suspect'. That is, me (Jan Fryer).
They all look alarmingly different to me, but Jan is unperturbed. What did the witnesses think of it all? Well, they disagreed on my height, weight, hair colour, complexion, jaw, cheek bones, ears, mouth, jewellery, clothes, indeed, pretty much everything. But it turns out the one thing they were happy with was their pictures - even when I met them afterwards. 'Oh yes! That's exactly as I remember you!' they chorused in front of their wildly different pictures. 'But it doesn't look anything like me!' 'Maybe not, but it is how we remember you.'
And that, as we now know, is all that matters. "

Link: http://www.dailymail.co.uk/news/article-1186754/Call-likeness--criminal-Just-accurate-artists-sketches-suspects.html