Court-date SMS reminder pilot

What we already know

Court-date SMS reminders are one of the most-replicated civic interventions. Across multiple US jurisdictions and UK courts, simple day-before reminders reduce failure-to-appear (FTA) by 4–8 percentage points off baselines of 15–35%. Effects are larger when reminders include the consequences of missing the date and when the message arrives at a useful time (early evening the day before).

Hypothesis

Defendants who receive an SMS reminder 18–24 hours before their scheduled court date will be 4–8 percentage points more likely to appear than defendants who do not.

Intervention

Send each defendant in the treatment arm a single SMS the evening before their court date. Include date, time, courtroom, and a one-sentence statement of consequences for missing the hearing (e.g. 'a warrant may be issued'). Do not include personal case details beyond the hearing time.

Comparison / control

Defendants in the control arm receive standard court communication only (the existing summons / hearing notice mailed at scheduling).

Outcomes

Primary

Court appearance rate at the scheduled hearing (binary: appeared / did not appear).

Secondary

• Warrants issued
• Subsequent failure-to-appear at rescheduled hearings
• Time-to-rescheduling for FTA cases

Required sample size

Computed for α = 0.05, 80% power, balanced allocation. Pick the row whose baseline best matches your jurisdiction, then size at the MDE you can defend.

Need a custom value? Use the sample-size calculator.

Randomization

1. Collect the list of defendants with hearings scheduled in the trial window (3–6 months, depending on case volume).
2. Stratify by hearing type (traffic, misdemeanor, civil), since baseline FTA rates differ substantially.
3. Within each stratum, randomly assign defendants 1:1 to treatment (SMS) or control (no SMS).
4. Use a reproducible random seed and log the assignment table so allocation is auditable.

Data collection

1. Daily after the trial start: pull the day's docket and join to the assignment table.
2. Record appearance status for each defendant at the end of their hearing date.
3. Capture rescheduled date if defendant did not appear.
4. Lock the dataset 30 days after the last scheduled hearing to allow late administrative updates.

IRB / ethics

Most municipal court IRBs treat this as minimal-risk and exempt research. The reminder is informational (no withheld services), the comparison arm receives standard process, and contact info is already in court records. Confirm with your jurisdiction's research review office. If sending to defendants in domestic-violence cases, exclude or apply additional safeguards.

Common pitfalls

• Wrong phone number: ~10–15% of defendant phone numbers are stale. Track bounces and report them; don't quietly drop them from analysis.
• Same-day rescheduling: if hearings get moved without the SMS being re-sent, treated defendants effectively become control. Decide in advance how to handle this and stick to it.
• Spillover: in small courts, court staff may notice the pattern and adjust behavior. Less likely below city-of-50k scale.

Anchor evidence — registry entries this template draws from

• Court Date SMS Reminders to Reduce Failure to Appear

  City of New York / ideas42 · New York City, NY, United States · 2015 · Effect: FTA reduced by 21%; equivalent to 30,000 fewer arrest warrants annually if scaled citywide

• Personalized SMS for Court Fine Repayment

  UK Courts Service / Behavioural Insights Team · United Kingdom · 2012 · Effect: Personalized SMS with debtor's name: £12.87 average payment vs. £4.46 control (189% increase)

Adopt this template

Tell us your context and we'll adapt the template to your jurisdiction and help you launch. No obligation. Small pilots are typically free.