Variability in Judgments: Why It Can Be So Hard to Find Consistency

The doctrine of stare decisis asks judges to treat like cases alike. “The term comes from the Latin phrase stare decisis et non quieta movere, which means ‘to stand by decisions, and not to disturb settled points’”. – The Honourable Justice Malcolm Rowe and Leanna Katz

Given the simpleness of the doctrine of stare decisis, you would think it would be simple to apply every time. And we would see the same outcome for similar cases every time. After all, stare decisis allows people to know the law by providing consistency, certainty, and predictability. But each case raises unique facts, and “the weight attached to precedent cannot be reduced to a set of mechanical rules…blind adherence to stare decisis can perpetuate unjust rule and can conflict with the purpose of the doctrine itself”. (Justice Sharpe in the book Good Judgment: Making Judicial Decisions)

In addition to the uniqueness of each case, external factors also add to the inconsistency between similar cases. In Noise: A Flaw in Human Judgment, authors Daniel Kahneman et al, note that mood, memory, hunger, fatigue, weather, and the order that cases are heard in can all cause variations in judgment. For example, professionals who make a series of decisions in sequence may try to restore the balance after a series of decisions that go in one direction. This is illustrated by asylum judges in the United States. These judges were found to be 19% less likely to grant asylum to an applicant when the previous two cases were approved.

Another example of external factors influencing judgment is hunger. A study of Israeli judges found that the likelihood of a favourable ruling for parole is greater at the beginning of the work day than at the end. Similarly, a favourable ruling is more likely after a food break than later on during the day.

Although inconsistency in judgments cannot be wholly eliminated, we can still work towards improving consistency within the judicial system. Currently, PhD Candidate Jon Khan is working on addressing this exact problem by looking at how to “improve judicial decision-making by making it more consistent, predictable, timely, and less prone to cognitive bias and heuristics; improve judicial decisions’ structure, accessibility, content, timeliness, length, and data-richness”. I highly recommend reading his work to learn more. (See: Deliberate Legal Design Website – / LLM Thesis –



  1. One of my favourite examples of success in bringing consistency to law is the Spousal Support Advisory Guidelines. Decisions about spousal support (alimony) used to be all over the map. Two visionary law profs (Carol Rogerson and Rollie Thompson) surveyed the law, consulted widely across the country, and created a series of formulas that have gone a long way to creating consistency and predictability. Interestingly, neither the executive, nor the legislature, nor nor the judiciary took the lead in this process.

  2. @Noel Semple. Fantastic example that I’ve been overlooking. It’s also a very early example of great legal “tech” with DivorceMate. Your point about who did it is great: we know courts often don’t have the capacity. But you’d think the executive and legislature might. So why isn’t it a priority? (Great example of what governments could do right here: Of course, law commissions could also be doing this with more funding. The CJC also has an obligation to “promote efficiency and uniformity, and to improve the quality of judicial service, in superior courts.” But perhaps they don’t believe that efficiency and uniformity include consistent judicial outcomes.

    I continue to wonder if people believe three things:

    (1) more consistency isn’t a good goal; it stagnates progress (of course, “a series of formulas” isn’t appropriate in all kinds of cases, like novel, viable Charter arguments perhaps;
    (2) cases are too special for a “series of formulas”; and
    (3) “a series of formulas” or more standardized approaches to decision making are civil law concepts.

    Lots of answers to all those arguments coming from me soon.