Bright-Line Rules: How to Banish Bad Habits

In 1966, the police arrested a man by the name of Ernesto Miranda in Phoenix, Arizona. They suspected Miranda of kidnapping and raping an 18-year-old woman 10 days earlier. And after two hours of interrogation by police officers, Miranda admitted to the rape charge and signed a confession.

But there was a problem. During the interrogation, the police never told Miranda about his right to legal counsel. They didn’t tell him about his right to remain silent and that they would use his statements against him.

When the case went to trial, the court used Miranda’s confession paper as evidence and quickly convicted him. But, since the police hadn’t informed Miranda about his rights, his lawyer objected and claimed that the confession was not fully voluntary.

The Miranda Warning

The Arizona Supreme Court upheld the decision, but the case eventually made it all the way to the U.S. Supreme Court where they overturned Miranda’s conviction because1:

“The person in custody must, prior to interrogation, be clearly informed that he has the right to remain silent, and that anything he says will be used against him in court; he must be clearly informed that he has the right to consult with a lawyer and to have the lawyer with him during interrogation, and that, if he is indigent, a lawyer will be appointed to represent him.”

With that, The Supreme Court had created a so-called bright-line rule2; a clearly defined rule or standard that leaves very little wiggle room. In other words, it’s a rule that establishes a bright line for what is allowed and what is not.

If a police officer doesn’t inform a criminal suspect of their rights, then the defendant’s statements are not admissible in court. And that’s why, ever since the Miranda decision, US police departments are required to inform arrested individuals using the Miranda warning3:

“You have the right to remain silent. Anything you say or do can and will be used against you in a court of law. You have the right to an attorney. If you cannot afford an attorney, one will be appointed to you. Do you understand these rights as they have been read to you?”

Bright-Line Rules for Life

So, what does all this have to do with bad habits? Well, it turns out that bright-line rules can be just as useful in everyday life. Take, for instance, the following examples:

  • I want to eat less candy.
  • I want to cut down on coffee.
  • I want to waste less time on social media.

These are all good intentions, but they’re also very vague. Consider, in contrast, the following alternatives:

  • I never eat candy at work.
  • I don’t drink coffee after lunch.
  • I only check social media once a day.

These statements establish bright lines. They make your intentions specific and measurable. And, as I’ve covered in a previous article, what gets measured is what gets improved.

You can also use bright-line rules to phase out bad habits gradually. If you, for example, want to quit cigarettes, you can allow yourself to smoke one cigarette less each week until you’ve kicked the habit.

Obviously, this strategy won’t produce perfect results. You might break your rules now and again. But at least you’ll know when you crossed the line. And that will make it much easier to correct the behavior going forward.

(Oh, and in case you wondered, Ernesto Miranda didn’t escape prison for long. He was sentenced to 20-25 years in prison for a robbery he committed during a separate crime.)

Do you want to master your habits? Get my book The Habit Blueprint.


  1. Miranda v. Arizona
  2. Bright-Line Rule
  3. Miranda Warning

Thank you to James Clear for writing about bright-line rules as a strategy for behavior change in Atomic Habits.