On Friday, exactly six months after Nancy Guthrie was abducted, police released two ransom notes in the hope that they would help identify her kidnappers.

Guthrie, the mother of US news presenter Savannah Guthrie, was 84 when she went missing from her Arizona home in January.

Her disappearance sparked a months-long investigation which has turned up few apparent leads and fewer suspects.

So how could Nancy Guthrie’s kidnapper, or kidnappers, be caught from these brief ransom notes?

The first of the notes, which are being treated as apparently credible, demanded millions of dollars in Bitcoin. The other claimed Guthrie died shortly after she was taken.

While the language in the notes might seem straightforward, police said the writer’s “distinct linguistic characteristics” may be recognisable.

“There are a number of pieces of information in these notes that just might jar someone to say ‘you know, I’ve heard that’,” said Pima County Sheriff Chris Nanos.

A forensic linguist told the BBC it’s possible to glean crucial information about a person from just a few sentences.

“It’s built upon the premise that we each carry an idiolect, or a word print, of our own that distinguishes our language from others,” said William Eggington, a retired linguistics professor from Brigham Young University who is now a forensic consultant.

But, he said, investigators have to hold scientific scepticism when they analyse notes like this – especially when they have so few words to work with.

Furthermore, they have to account for the possibility that the person may be trying to disguise their natural writing voice.