Ask two people the same question: "why did this happen to you?" and you'll often get two structurally different kinds of answer. One person reaches for things they did: choices, effort, mistakes, decisions that led to the outcome. The other reaches for things that happened to them: luck, timing, influential people, forces outside their hands. Neither is wrong about their own life. But the difference between them is one of the most durable findings in personality psychology, and it has direct consequences in a jury box.
The construct is called locus of control, and it has been measured for sixty years.
Rotter's original insight
In 1966, Julian Rotter published a monograph that introduced the idea of generalized expectancies for internal versus external control of reinforcement — locus of control, in the shorthand that stuck (Rotter, 1966, Psychological Monographs, 80(1), Whole No. 609). His claim was that people develop a stable, generalized belief about the relationship between what they do and what happens to them. Someone with an internal locus of control believes outcomes flow largely from their own behavior and characteristics. Someone with an external locus believes outcomes are governed by luck, fate, or other people who hold the power.
Rotter built a scale to measure it, and the construct turned out to be remarkably robust — it predicts behavior across domains as different as health, academic achievement, and workplace performance, and it does so decades after he first described it. It is not a mood or an opinion. It is closer to a lens: a stable default for how a person explains the relationship between action and consequence.
The refinement that matters
Rotter's original scale treated locus of control as a single line running from internal to external. Hanna Levenson's work, presented in 1973, showed that "external" is actually doing two different jobs at once, and that splitting it apart matters (Levenson, 1973, "Reliability and Validity of the I, P, and C Scales," ERIC ED087791).
Levenson separated external control into two distinct beliefs: control by powerful others — specific people or institutions who hold sway over your outcomes — and control by chance — impersonal luck, fate, randomness. The resulting three-dimensional model captures something the single line misses. Two people can both score "external," but one believes the deck is stacked by powerful institutions while the other believes the universe is simply random. Those are not the same person, and they do not reason the same way about a defendant.
This distinction is not academic hair-splitting. It is exactly the kind of difference that determines whether a juror hears "a hospital cut corners" as plausible or paranoid.
Why it lives in a jury box
A personal injury case is, at its core, a contested story about causation, about who or what was steering when the harm occurred. The plaintiff says: this happened to me, through no fault of my own, because someone with power was careless. That is, structurally, an external-locus story. It asks the jury to accept that forces outside the plaintiff's control produced the injury.
A juror with a strong internal locus of control hears that story through a particular filter. Their generalized expectancy — the one Rotter described — is that people's outcomes track their own choices. Confronted with a plaintiff who says "I had no control over this," the internal-locus juror is predisposed, not out of malice but out of stable disposition, to wonder what the plaintiff could have done differently. The same set of facts that reads as misfortune to one juror reads as unexamined personal responsibility to another, and the difference between them was set long before they entered the courtroom.
What the research actually shows
The most direct empirical evidence connecting locus of control to juror decision-making comes from Butler and Moran's 2007 study of 212 jury- eligible participants in Florida (Butler & Moran, 2007, "The Impact of Death Qualification, Belief in a Just World, Legal Authoritarianism, and Locus of Control on Venirepersons' Evaluations of Aggravating and Mitigating Circumstances in Capital Trials," Behavioral Sciences & the Law, 25(1), 57–68).
The headline finding is one most people wouldn't predict. Butler and Moran found that jurors who were death-qualified, e.g. the ones who pass the screen to sit on a capital jury, were significantly more likely to have an internal locus of control. That pairing is its own small revelation. The juror who believes outcomes flow from individual choices is also the juror most willing to impose the ultimate consequence for those choices. The worldview is internally consistent: if people steer their own lives, then people who steer toward harm should answer for it.
The more specific finding is the one that matters most for plaintiff work. External-locus jurors in the study were significantly more likely to endorse statutory mitigators — the legally-recognized reasons to extend mercy that involve diminished agency: mental or emotional disturbance, duress, inability to appreciate the criminality of one's conduct. They were not particularly more receptive to nonstatutory mitigators like a history of alcoholism or military service. The pattern is precise: externals don't just feel "softer" on defendants in general. They respond specifically to the kinds of mitigation that match their worldview about how outcomes happen — forces acting on a person, not choices made by one.
That is exactly the structural feature that makes locus of control useful as a juror attribute. It does not predict a verdict. It predicts which arguments will land. For an attorney trying to humanize a plaintiff whose own conduct is in the contributory negligence crosshairs, the external-locus juror is the one most receptive to "the circumstances overwhelmed them." For the same case, the internal-locus juror is the one who needs a different bridge entirely.
Butler and Moran's study was a capital case rather than a civil injury case, and the same caveats apply that always apply to translating between settings. But the underlying mechanism — locus of control acting as a stable filter on how jurors weigh evidence about agency and responsibility — is the same mechanism every personal injury attorney encounters every time they pick a jury.
What it does not do
Locus of control does not set a verdict. It is one filter among several, and Butler and Moran's own data make this clear — legal authoritarianism was a stronger predictor across more outcomes in their study than locus of control was. A juror's actual response emerges from how their locus of control interacts with their moral foundations, their just-world beliefs, their authoritarianism, and their own life history. A juror can hold a strongly internal locus and still find for a plaintiff when the evidence of institutional carelessness is overwhelming. The construct tells you where the friction will be, not what the answer must be.
That is the honest version of what a measured attitude can do. It is more useful to a trial lawyer than a false promise of certainty.
If you want to see how a panel from your venue divides along this axis, the form on the homepage is the way.