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 – https://www.deliberatelegaldesign.com/whats-the-problem / LLM Thesis – https://bit.ly/3ylaiii).