Applying the New Science of Metaphors to Forensic Science Testimony

Thu, 10/18/2012 - 10:46am
Ronald K. Bullis, Ph.D., J.D.

Using metaphors to explain concepts and data enhances the scientific testimony’s impact, meaning, and memory-value.

All thinking is metaphorical.
Robert Frost, (quoted in Shibles, 1974)

Forensic scientists are increasingly required to testify about their findings and their professional conclusions.1 To present clear and compelling testimony, forensic experts need more than their science training. They need effective and evidence-based communication skills. This article describes and illustrates why metaphors are such powerful vehicles for scientific testimony and presents a simple, but extremely effective method to offer clear and compelling forensic science testimony.

Forensic scientists are like translators. They must “translate” scientific procedure and opinion in ways that both educate and persuade jurors. Legal scholars recognize that narrative elements, such as metaphors, effectively negotiate those two world-views, language, and goals.2

Science, especially neuroscience, also tells us that metaphors function as significant cognitive tools for data interpretation and decision-making.3 Lawyers, politicians, war planners, peace planners, advertising and PR professionals, and psychotherapists have long used metaphors as tools to inform and to influence how people frame issues, prioritize choices, and calculate results. Metaphors have climbed out of literature courses and into court testimony.

Neuroscience and Using Forensic Metaphors
Metaphors associate dissimilar concepts across areas of the brain associated both with affect and cognition. The images used in metaphors connect to our own images to form powerful and persuasive cognitive associations. First, they collect neurons together to form constellations of images. “Neurons that fire together, wire together” is the most famous adage in neuroscience.4 It means that images and metaphors that ignite memories, thoughts, and feelings bundle together to form constellations of much more powerful thoughts. Because this bundling of neurons takes place across a wide area of the brain, the impact of the metaphor increases geometrically.

The following trial excerpt5 depicts how one forensic scientist explained the role of DNA to the jury under direct testimony.

Prosecutor: ...But what is DNA? I mean, we—we know it’s out there. What is it?
Forensic scientist: …It controls how you develop and function. You inherit half your DNA from your mother and half from your father, and the inherent DNA will stay the same throughout your lifetime.

Can you spot the metaphor? “Controls” is not a scientific analysis or description of how DNA works. “Controls” is a metaphor for how DNA works. It’s a metaphor because it connects two different images. We “control” our car. We “control” our TV remote. When the scientist used “controls,” they tapped into all jurors’ images of “control,” so that DNA doesn’t just equal “control.” The metaphor equals all the jurors’ expectations, memories, and motivations for controlling. The use of “control” now clusters with every other neuron connected to “control” in the juror’s mind. Like a word search on the internet yielding a zillion “hits,” the image expands itself ad infinitum. The well-placed metaphor goes viral in the mind of jurors in seconds.


Metaphors are powerful testimonial tools for three reasons. First, metaphors can transform how jurors “frame” or understand and consider trial issues.5 Metaphors provide the cognitive infrastructure into which ideas and data will be stored and understood. Jurors use metaphors as “frames” into which they “fit” evidence and testimony. Forensic scientists who use forensic metaphors marshal neuroscience to clearly and convincingly define the role and significance of their testimony.

Second, metaphors “reframe” images and incite thinking “outside the box.”6 Metaphors, in connecting dissimilar images, expand and “morph” the meaning of both images. Forensic scientists may urge jurors to think in new and different ways. After all, jurors consider facts from different perspectives offered from different parties in court. In the “control” metaphor above, the jurors’ minds pave new pathways for the significance of DNA as well as the significance of DNA evidence for their particular case. Metaphors are perfect vehicles by which to “try on” evidence using different images.

Third, metaphors enhance meaning and meaning enhances memory.7 Metaphors enhance meaning and the more meaningful a concept, the more memorable it is. The more a juror understands about the importance of scientific testimony, the more they will remember it. Ideas connected to images make it easier for our brains to remember names, numbers, faces, even events. The more jurors integrate forensic testimony into their own concepts and understanding, the more they will recall that testimony in their deliberations. When Winston Churchill used the metaphor, “Iron Curtain,” to describe the Berlin Wall, it stuck in the mind of strategic planners, the voting public, and politicians for over half a century.

Applying Metaphors for Clear, Compelling Testimony
Scientific testimony can seem unfamiliar and esoteric to jurors. A scientist who tries to explain science with more science piles confusion upon confusion. After all, the scientist has invested years in education and training to learn his or her protocols, techniques, and scientific judgment. Probably every juror has heard of DNA, but it is unwise to assume that jurors know its structure and function—let alone its particular significance to a particular case.

Yet, jurors are expected to assess the credibility of forensic scientists, to assess the value of their testimony to the case, and to prioritize scientific evidence to the case at hand. Also, jurors may labor under information from forensic science-inspired TV shows and movies that may or may not be accurate or applicable for their case.

Metaphors help. They neither “dumb-down” information nor change the science. They render technical information in a concise, clear, and compelling manner—if metaphors are used properly.

Research shows that the most effective metaphors are both familiar to the jury and appropriate to the issue at hand.8 The next two sections explain and apply these factors.


Using Familiar Metaphors
Effective metaphors place familiar faces on unfamiliar testimony. Unfamiliar scientific testimony is a problem. A solution is to explain science with evocative, familiar metaphors, such as in the following exchange.9

Court: Any voir dire?
Defense Attorney: No, Your Honor.
Court: Ladies and gentlemen of the jury, you will receive [scientist] as an expert in forensic science.
Prosecuting Attorney: Now, could you explain what DNA is?
Scientist: DNA stands for deoxyribonucleic acid. And basically DNA can be thought of as a blueprint for your body just as you have a blueprint to build a house that tells you where the walls and windows should go.

In using the “blueprint” metaphor to answer the question, this forensic scientist explained the function and importance of DNA evidence in a single sentence. While jurors may not know either the scientific name for DNA or its specific physiological function, they know what a “blueprint” is. If the scientist makes metaphors both familiar and fit the issue, they will be meaningful and memorable to the jury.

Using Relevant Metaphors
Relevant metaphors fit the right issue in the right case at the right time. Irrelevant metaphors confuse the testimony and confuse the jury. Here, the forensic scientist explains a concept that was a significant factor, both at trial and subsequent appeal.10

Attorney: Now, you testified that you followed the protocol. What does that mean in layman’s terms? I’m not—
Scientist: Right. Just like you have a recipe for telling you how to cook a—make a cake, we have recipes which tell us how to conduct the DNA testing. It is called a protocol then. It is a recipe.
Attorney: And that’s what you followed. Is that correct?
Scientist: Yes.

All scientists know the importance of protocols, but jurors may not. Calling a protocol a “recipe” evokes the connection between a protocol and a familiar set of important steps—following a cake recipe for example. The procedures are verifiable, clear, uniform, and measureable. A recipe is neither experimental nor arbitrary. Likewise, a protocol is the product of testing to verify its reliability and validity. Moreover, a number of jurisdictions follow the same protocol. Therefore, it is easy to verify its effectiveness in large-scale studies.

Finally, the “recipe” metaphor evokes a “tasty” product, yielding a satisfying, accurate result. Instead of belaboring the minutia of protocols, the well-placed metaphor drives home the protocol’s characteristics and its significance cogently and compellingly.

Continuing Education for Forensic Scientists
We use metaphors every day. Every time we give or accept flowers, daydream about a new car or a new home, or watch commercials on TV we create and apply metaphors. We use metaphors to describe movies, vacations, and sometimes, our bosses! Forensic scientists use forensic metaphors in a specific way. Creating and applying forensic metaphors is both an analytical and imaginative process. This is a learned process.


Here are a few hints on creating effective metaphors.

  1. Clearly define the point of the scientific testimony. Will it describe the reliability of the method? Will it have to define scientific concepts (such as DNA or protocols) or will it have to describe the method of data collection?
  2. Now, let your mind wander a little (“free association” as Freud called it).
  3. Use “like” or “as” to link one image with another. For example, “blood pattern analysis is like…”
  4. Make a list of possible metaphors.
  5. Finally, use analytical skills to determine which metaphor is most familiar and appropriate to use with a particular issue, a particular case, and a particular jury.

Neither the importance of scientific data nor its relationship to the trial issue are immediately recognized or valued by jurors. The best science in the world is lost when jurors misunderstand its content or significance. Using metaphors to explain concepts and data enhances the scientific testimony’s impact, meaning, and memory-value. Metaphors don’t change the science or dumb it down. They make science clear and compelling.


  1. See Bullis, R. (2012). Stressing Demeanor Credibility: Continued Impacts of Melendez-Diaz for Forensic Scientists in Forensics Magazine, 9(1), 15-20 and Bullis, R. (2011). Applying Melendez: Briscoe and beyond Forensics Magazine, 8(3), 15-20.
  2. Caudill, C. (2002). Scientific narratives in law: an introduction. Law and Literature, 14, 253; Rideout, J.C. (2010). Penumbral thinking revisited: metaphor in legal argumentation. Journal of the Association of Legal Writing Instructors, 7, 155.
  3. Boroditsky, L. (2011). How language shapes thought. Scientific American, 304(2), 62-65 and the pioneering work in Lakoff , G. & Johnson, M. (1980). Metaphors we live by (University of Chicago: Chicago).
  4. D.O Hebb’s 1949 famous quote in Organization of Behavior: A neuropsychological theory (John Wiley & Sons, Mahwah, NJ).
  5. Virginia v. Winston, 404 S.E.2d 329, Va. App. Lexis 80 (1991) trial transcript pp. 321, lines 9-17 found in problems.
  6. For a comprehensive description of how metaphors “frame” issues and persuade audiences and consumers see Geary, J. (2011). I is an Other. (HarperCollins: New York). For an empirical test on the how metaphors “frame” issues see Williams, A., Davidson, R. & Yochim, E. (2011). Who’s to blame when a business fails? How journalistic death metaphors influence responsibility attributions. Journalism and Mass Communication Quarterly, 88(3), 541-561.
  7. Modell, A. (2003). Emotional memory, metaphor, and meaning. Psychoanalytic Quarterly, 555-568.
  8. Thibodeau, P. and Durgin, F. (2011). Metaphor Aptness and Conventionality: A Processing Fluency Account. Metaphor and Symbol, 26, 206–226.
  9. Lovitt v. Virginia, 537 S.E.2d 866, Va. Lexis 149 (2000) cert. den’d, 534 U.S. 815 (2001), trial transcript p. 1157, lines 18-23 found in problems.
  10. Supra, note 9, trial transcripts p. 1190, lines 9-18.

Ronald K. Bullis, Ph.D., J.D., teaches law at Averett University and is a practicing psychotherapist. He writes on law, malpractice, forensics, and the use of narratives in the courtroom. He conducts seminars on law, professional liability, and ethics and can be reached at


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