Forensic Linguistics

In 1952, a man named Derek Bentley was trialed and ultimately sentenced to death for the murder of a policeman. In 1993, Bently received a posthumous (after death) royal pardon, and his name was cleared. Although pardons are not uncommon, this one was unique as it was one of the first times in history forensic linguistics was responsible for the pardon. The linguist Malcolm Coulthard studied Bentley's confession and found several instances in which the language within the letter was inconsistent with Bentley's idiolect (personal use of language). This led prosecutors to rule that the confession had been tampered with by the police. This is a perfect example of forensic linguistics.

Today, forensic linguistics has multiple branches and is used by many different experts for purposes such as criminal investigations, trials, examining the language used within law, and more.

Forensic Linguistics Definition

Before we look at the purpose, history, and some example case studies of forensic linguistics, let's look at a basic definition:

Prosecutors and lawyers can use forensic linguistics when compiling evidence to help them prove who is innocent and who is guilty based on idiosyncratic language use (such as in the case of Derek Bentley); however, this isn't the only use of forensic linguistics. Typically speaking, forensic linguistics covers three main areas of study:

• The language used in written law (e.g., the semantics behind a written law can impact someone's verdict).
• The language used in the judicial and forensic process (e.g., the language used by police during questioning, for example, did they use leading questions?).
• Linguistic evidence (e.g., comparing writing styles in presented evidence to the writing styles of the accused).

Let's now look at the history behind forensic linguistics before taking a closer look at each of these areas of study.

History of Forensic Linguistics

The history of forensic linguistics can be traced back to a case in the USA in 1927. A ransom note to a man named Duncan McLure from an apparent stranger spelled Duncan's last name in a way that only a close friend or relative would know how. Duncan was the only person in the family to spell his name McLure instead of McClure. This linguistic mishap revealed the writer of the ransom note to, in fact, be a member of Duncan's family.

Further calls for linguistic forensics were made in the USA in the mid-1900s due to lexical ambiguities within the Miranda warning. A Miranda warning in the USA reminds you of your legal rights. Police officers in the USA often relay them to you after they detain you during a criminal investigation. Several concerns were raised about whether people across the country could actually understand the language used within the Miranda warning, and in 1966 the language was standardized in English. Today, similar questions are raised when dealing with non-native English speakers.

In the UK, forensic linguistics began growing in popularity due to the mounting distrust in the authenticity of police statements. It was found that the police were not presenting suspects or witnesses' statements in a complete or truthful way, and linguistic information that we would now deem to be essential, such as pauses, backtracking, and minor details, was often missing.

In 1968, the linguist Jan Svartvik first used the term forensic linguistics in an official capacity in his book The Evans Statements: A Case for Forensic Linguistics. Svartvik conducted a linguistic analysis of Evan's police statements, a man accused of murdering his wife and child, and he found many inconsistencies between the grammatical style and register of the statements and Evan's usual writing style.

Fig 1. - Forensic linguistics deals with the language of the law.

Branches of Forensic Linguistics

As we mentioned, there are three main branches of forensic linguistics:

• The language used in law

• The language used in the judicial and forensic system

• Linguistic evidence

Language used in Law

One of the smaller fields of study in forensic linguistics is the language used in the written laws themselves. Written laws can often be lengthy, complex, and old (for example, there are some laws still in place in the UK that were written in 1267!); because of this, laws can often be filled with lexical ambiguities.

Forensic linguists or lawyers may look for ambiguities within laws to help prove their cases.

It is widely known within the field of law that these lexical ambiguities exist, and rules, such as the rule of lenity, have been put in place to help mitigate their impact. The rule of lenity states that any lexical ambiguities must be interpreted in the way that is most favorable to the defendant (the accused).

Language used in the Judicial System

This branch of forensic linguistics is concerned with the language used by the people who work within the law, such as police officers, lawyers, barristers, attorneys, judges, government leaders, etc. Sometimes people can use language in certain ways to elicit answers they want or to "trick" and confuse others. Forensic linguists aim to reveal these language uses and bring transparency to the legal process.

Some language techniques forensic linguists may be interested in include:

• Leading questions - These are suggestive questions that lead the interviewee to give a pre-determined answer. E.g., "And how angry would you say you felt at the time?"

• Speech accommodation - Speech accommodation is a theory that suggests people change their speech to be more relatable to the person they're talking to. Howard Giles et al. found that professionals working within the law, such as the police, change their speech to closer resemble others in order to build trust.¹

• Use of closed or open-ended questions - Let's look at an example for this one. Imagine a witness being questioned by a lawyer on the stand (i.e., in front of a jury). If the lawyer wanted the witness to accidentally say something they're not supposed to, they might ask lots of open-ended questions to get them to talk a lot. However, if the lawyer doesn't want the witness to accidentally say something, they might ask lots of closed-ended questions (for example, questions that can be responded with using a yes or no) to ensure they talk as little as possible.

• Use of jargon and terminology - Sometimes, professionals working within the law will use specific jargon and terminology to deliberately confuse others.

Linguistic Evidence

When linguistics forensics is used to analyze evidence, the grammar, syntax, register, tone, register, and dialectical or idiolectal elements of language are compared to the usual language patterns of the accused/witness/victim.

Before we look at the type of forensic texts, let's unpack some of those terms.

• Syntax: The arrangement of words and phrases in a sentence.

• Register: The style and formality of language.

• Dialect: A language variety that may differ from the "standard" form. For example, someone from the north of England may use English slightly differently than someone from the south.

• Idiolect: A person's unique use of language. This comprises the dialect they use, their accent, their speech patterns, their vocabulary, and more.

The types of forensic texts that may be analyzed by a forensics linguist include:

• Witness statements

• Confessions

• Ransom or threat letters

• Phone calls to the emergency services

• Suicide notes

• Death row statements

• Social media posts and text messages

Fig 2. - The linguistic style of social media posts is now commonly considered when looking for evidence.

Forensic Linguistics Methods

Let's now look at the different methods used within forensic linguistics.

Comparative Linguistics

Comparative linguistics, aka forensic stylistics, is the process of comparing one text to another and looking for similarities or differences in linguistic style. This could include things such as:

• Vocabulary choice, e.g., The greetings and sign-offs in emails could be compared.

• Use of certain idioms or phrases.

• Spelling, e.g., Does the text use standard British, American, Australian, etc. English?

• Use of slang.

• Use of capitalization.

• Citation and referencing style (applicable for academic texts).

• Consistent mistakes, e.g., spelling mistakes or incorrect use of commas, etc.

• Date format. There are several different ways to write the date.

All of these lexical items, and more, can combine to form a person's idiolect. Comparative linguistics involves looking for evidence of a person's idiolect.

Linguistic Dialectology

Linguistic dialectology involves studying language to look for dialectal clues, i.e., where the writer might be from or where they now live.

As an example, a person's accent or use of regional-specific vocabulary could provide insights into where they are.

Discourse Analysis

Discourse analysis is a broad term that can be applied in multiple ways across multiple disciplines. In linguistic forensics, discourse analysis can range from noting and analyzing discourse markers like false starts, stutters, backchanneling, and fillers (e.g., umm, uhh, wait...), to looking for wider hidden meanings within texts.

Author Profiling

Author profiling is the process of examining all the lexical items mentioned above and building a criminal profile from the evidence.

Read on to learn more about author and criminal profiling in the case of the Unabomber.

Forensic Linguistics Examples

Let's finish off by looking at some case study examples where forensic linguistics has played a significant role in the legal process.

The Unabomber Case

Throughout the 1970s, 80s, and 90s, a made named Ted Kaczynski anonymously sent multiple DIY bombs to random victims across the USA. He often targeted universities and airplanes and gained the nickname the Unabomber. Kaczynski was meticulous in ensuring he left no evidence, and for many years, the FBI had no forensic leads for catching him.

In 1995 a criminal profiler named James Fitzgerald started working on the case and began to study the letters that Kaczynski had sent to the newspapers about his crimes. From the letters, Fitzgerald was able to determine that Kaczynski was a well-educated man who likely lived alone. He also inferred that Kaczynski would be in his 50s due to the slang he used, he was probably born in Chicago due to his dialect, and he had likely written a Ph.D. in the 1960s due to the academic referencing style and layout of the letters.

This criminal profile was vastly different from the one the FBI had before the linguistic evaluation, but it turned out to be almost entirely correct.

In 1995, Kaczynski sent a 35,000-word manifesto to the FBI, which was then published in the newspaper in hopes that someone would recognize the Unabomber's idiolect and report him to the FBI. The tactic worked, and Kaczynski's brother came forward with hundreds of personal letters he had received from his brother over the years. This is where comparative linguistics comes in. Thousands of lexical matches between Kaczynski's personal letters and the manifesto were found, including unique spelling, vocabulary choice, slang, syntax, and more. However, there was one lexical item that helped cement the linguistic proof and encouraged the judge to sign off on the search warrant — an Early Modern English proverb.

In both the manifesto and a personal letter, Kaczynski used the Early Modern English proverb, "You can't eat your cake and have it too," rather than the Modern English version of "You can't have your cake and eat it too." (Notice the change in syntax?) This idiolectal use of a common proverb ultimately helped give away his identity. Pretty cool, huh?