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Playing Cluedo with speech sounds

Using speech analysis to resolve crimes. That's what Meike de Boer (26) is aiming to do with her PhD research. 'By analysing how a person pronounces "eh", you can help identify that person; hopefully even when that person speaks different languages.'

Over twenty thousand telephone conversations are tapped every year in the Netherlands by investigation services. But how can you be sure that the person you're listening to is the actual suspect? What about if his or her voice is disguised? Or if the suspect claims that somebody else made the call using his phone? Forensic linguistics can provide the answer. With her PhD research, Meike de Boer is working on improving this method of investigation. 

‘The sound eh is key to my research,' De Boer explains. I take measurements of sound recordings of eh: how long they are, how they sound, what is the pitch? The specific question I want to answer is whether the language that the person is speaking has an influence on these factors. Or, do people say eh the same way in different languages?' Forensic linguistics is a relatively new field: the more scientific evidence there is, the better speech recognition can help trace or exclude suspects.  

De Boer had a strong sense of right and wrong even from a very young age. 'As a child I believed it was important to stick to the rules. If I was cycling to school with a friend and her mother, and they rode through a red light, I wouldn't do that.’ That sense of keeping to the law was what gave me the idea that I wanted to join the police. 'I went to some open days at the police academy, but the sports test put me off. Not only that, I close my eyes a lot if I'm watching a police series because it's too scarey.' 


After a slight detour via medicine ('that was the best match for my exam profile') De Boer found her way into Communication and Information Sciences at the Vrije Universiteit (VU) in Amsterdam. ‘I definitely preferred my second choice, but after a while I missed the sense of social relevance. That is, until we came to the Forensic Linguistics part of the programme: in this course, I was able to use my knowledge in forensic applications.' 

That inspired De Boer to also start studying Criminology and to take a master's in Psychology of Law in Maastricht. When she had almost finished her master's, she heard about the new master's in Forensic Linguistics at the VU. Without even realising it, that was exactly what she had been waiting for. 'After studying for six years, finally I was able to do what I really wanted.' Even before completing this master's, one of her lecturers pointed her towards a PhD position in Leiden. 'They were looking for a candidate who had already got a master's in Linguistics, which I didn't have yet, and my  main  focus was on written text.' Still, she decided to apply. When she was asked during the interview whether she had experience with experimental phonetics. De Boer was sure she didn't stand a chance. 'I had completely the wrong background, but they actually split the position so that they could offer me a place.' 

Science writing

De Boer's ambition, once she has her PhD, is to work for the Netherlands Forensic Institute. 'Ideally I'd like to be involved with cases as an external linguistics specialist so that I can further my scientific career and apply my knowledge in practice at the same time.' But she also wants to write popular scientific articles about eh. 'It's a sound that nobody ever thinks about, and yet everyone uses it!'   

Text: Wilke Martens
Photo: Taco van der Eb

This article has appeared in Leidraad, the alumni magazine of Leiden University. Read the complete article online (inn Dutch).

What is... forensic phonetics?

Forensic phonetic looks at differences in the way people produce speech sounds. If we can be certain about how a person speaks or pronounces particular sounds, this can help to identify that person. This can be useful in forensic investigations if an anonymous telephone conversation is tapped and it is important to know whether the person speaking is the suspect or someone else.

Forensic phonetics is a subset of forensic linguistics. This field combines both the law and language, varying from the language of the police, lawyers and judges to the way language can serve as evidence in a legal case.   

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