Who, what, why: How do you identify a mystery person?

image captionThe boy said he had been living in the German forest for about five years

German police are trying to identify a teenager who appeared in Berlin saying he had been living in the woods for five years. So how do you go about identifying a mystery person?

The story of an English-speaking boy who emerged after five years living in a German forest has captured the headlines.

Referred to as "forest boy", he is thought to be about 17, and speaks some German, as well as his English. He has told police that he and his father went to live in the woods after his mother died, but cannot remember where he came from before then.

He told police his father had died in the woods and he had buried him in a shallow grave, before walking for two weeks to reach Berlin to seek help. He says his name is Ray and thinks he knows his date of birth, but that is all police have to go on. So how will they go about trying to find out who he is?

Police will use a combination of forensic analysis, interview techniques, official documents and publicity to try and identify who the teenager is, says criminologist and child protection expert Mark Williams-Thomas.

The starting point is forensic analysis of his DNA, fingerprint and dental records to see if they can establish who he is. In this case forensics may not throw up any clues because the boy is so young.

Next officers will need to interview him extensively to gain as much information from him as he is able or prepared to give, says Williams-Thomas.

"If the information is credible this could lead them to some obvious points to start, like birth records, missing persons reports."

They will want to trace the teenager's steps back to the place where he has spent the past five years. This could throw up vital clues, such as items of clothing or tools he has used to survive, even people who may have fed him at some point.

This could also help ascertain whether the boy's father has been buried in the woods, and if they do find a body, they will be able to do DNA testing on it. There is far more chance the father will be on police databases because he is a lot older, says Williams-Thomas.

He says it is crucial that a British police officer interview the boy as soon as possible.

"They will have the knowledge to identify his accent. They may also be able to pinpoint where he is originally from in the UK. Details that might be meaningless to German police could be picked up by British officers. The boy might, for example, remember living in a place with a cathedral."

But a spokesperson for the German police told the BBC that it was too early to tell whether the boy was British. She said he could be from any English-speaking country, or could have learnt English in Europe, such as in Spain or even Germany.

Dr Anja Lowit, a linguistics expert at the speech and language therapy division at Strathclyde University, says specialists will need to get a language sample from the boy.

"There are various papers available about different regional varieties of British and other types of English," says Lowit.

"Vowel differences are a good indicator of accent, and whether people produce glottal stops. In the longer sentences they can listen to his intonation patterns, which are quite distinctive for certain accents, and they would also notice any peculiar choices of words or grammatical forms."

But, she says that there is a level of difficulty because people speak with varying degrees of accents, so his might not be very strong. For example, she says children can also be influenced by their parent's accents or psychosocial issues - for example wanting to fit in with other children who speak in a particular way - so it's not straightforward to determine where someone comes from.

"If he's not English, his foreign accent can again give a hint, but there is a lot of overlap between different accents, and depending on how early and under what circumstances he learnt English, he might not present with the normal picture that one would expect."

image caption'Piano Man'' from Prosdorf, Germany, was found on a beach in Kent in 2005

James Law, professor of speech and language science at Newcastle University, says English is likely to be the boy's first language.

"It is unlikely he would have lost one language and not the other - that he would have lost the German and retained the English."

In 2003, Law worked with researchers on the case of Edik, a young boy in the Ukraine who was unable to speak because he spent more time with stray dogs than his often absent parents.

Although the boy in Germany says he cannot remember anything from his life before he went into the woods, Law says tests can be carried out to see how he responds to certain cultural references.

"They could put a lot of material in front of him, places, pictures, cultural references - such as children's TV characters from the period before he went into the woods. These things can be so potent to a child - they might get some spark of recognition."

Piano Man

Kent Police have dealt with two notable cases in recent years where unidentified people been found. Piano Man made the headlines in 2005 when he was found wandering on a beach.

His identity baffled hospital carers for months because he did not speak, just apparently played the piano. He eventually claimed his memory had returned and that he was in fact German.

A spokeswoman for Kent Police says it has no set process for dealing with such cases as they are very rare.

"In this case, for example, German police will probably be investigating to see if there is any connection with the British armed forces, many of whom are stationed in the country."

Another crucial element to such investigations are media appeals, say the experts.

"It is ultimately the most likely way he will be identified," says Williams-Thomas. "Just as public appeals are a great way of catching offenders, it is no different when you are trying to establish who someone is."

Ultimately, Williams-Thomas believes the boy will be identified.

"The fact that he is speaking is a massive bonus. The police will already have a lot to go on, even if they are not telling us. It's a case of piecing it all together, like building a jigsaw puzzle."