Almost 100 pages of abusive messages: Somewhere in them the truth was hidden.

As the threats continue to pile up, the language profilers work harder and harder. The Whatsapp messages now total almost a hundred pages. In poring over all the text, the analysts notice the author doesn’t distinguish between “a” and “an” when the next word begins with a vowel, as in “a ocean is not wide enough.” While the usage is not rare, it is not standard English. The investigators realize that Rosemarie Stack sometimes makes the same mistake, and they’re aware that anomalies of usage sometimes “wear off” on others, especially if they work together closely. Perhaps this is an indication that Stack and her stalker are workmates.

More interesting to the analysts is the author’s use of the word “unlovely.” One of the early messages just said: “Unlovely!” Another had said: “Looks like it’s going to end just as unlovely as all your other relationships,” and there were other instances as well. There are many other adjectives for expressing the same idea, such as “ugly,” “unpleasant,” or “unsightly.”

“LANGUAGE ALWAYS CONTAINS TRACES FROM THE PAST—AND THEY CAN BE TRACED BACK TO THE ORIGIN.”

Such seemingly unimportant speech codes (“a/an,” “unlovely”) ultimately led the investigators to a workmate of Rosemarie Stack—a male flight attendant. The investigators learned he’d felt an attraction for his female colleague over a period of many years but had never expressed it. He was determined that Stack was going to be his workmate and nothing more, and that’s the way things remained for a long time. Then the two of them had a long overlay with the rest of the crew following a long-haul flight. He’d showed his romantic interest for the first time, and Stack had responded positively. But when she later entered into a relationship with another man, the steward was hurt and offended and began keeping his distance from her. Yet his romantic feelings for her never died, and his disappointment eventually turned into the aggression seen in his Whatsapp messages.

“These were linguistic fingerprints that would not have held up in court,” says Martin. “But the evidence they provided was extremely useful to our investigation. For language always contains traces from the past—and they can be traced back to the origin.” The profilers laid out several pages of Whatsapp messages the stalker had sent next to the flight schedule of Rosemarie Stack’s colleague. They found the anonymous messages were always sent when the steward was on the ground. Stack never received any messages while he was in the air, but as soon as he landed somewhere they would start right up again. “You might say our investigation resulted in a belly landing for the jilted steward that fortunately came to pass before the situation could become a crash landing for Rosemarie,” says Martin.

The case of Rosemarie Stack is just one of the many that language pros Leo Martin and Patrick Rottler have cracked in the past few years. What they all reinforce: A seemingly insignificant phrase or sentence in an anonymous written message can contain consequential clues about the identity of the sender—provided one knows what to look for…