Appeal reversal probability estimator
Enter conviction type, years since trial, and the nature of any new evidence to see rough historical reversal rates drawn from UK Court of Appeal data. Built to give context, not legal advice.
Formula: Base rate × Time factor × Evidence multiplier
This is a rough statistical estimate derived from aggregated UK Court of Appeal data. It is not legal advice and cannot predict individual case outcomes. Always consult a qualified solicitor or barrister for appeal guidance.
How the calculation works
The estimator starts with a base reversal rate for your conviction type, applies a time decay based on years since trial, then adjusts for the strength of any new evidence. The formula is:
Reversal rate = Base rate × Time factor × Evidence multiplier
Base rates by conviction type
| Conviction type | Base reversal rate | Notes |
|---|---|---|
| Summary | 30% | Magistrates' Court; often procedural errors |
| Indictable | 18% | Crown Court; jury trials, higher burden |
| Either-way | 24% | Mixed category, intermediate rate |
Time decay
Appeals lose strength as time passes. The time factor is calculated as 1.0 − (years × 0.05), floored at 0.4. An appeal one year out retains 95% of its base rate; at ten years, only 50%; beyond twelve years, the floor of 40% applies.
Evidence multipliers
| Evidence type | Multiplier | Why |
|---|---|---|
| None / procedural | 1.0× | No boost; relying on trial record alone |
| Witness recantation | 1.3× | Credibility issues limit impact |
| Expert reinterpretation | 1.5× | Depends on field consensus and error clarity |
| DNA / forensic | 2.0× | Objective, reproducible, hardest to rebut |
What this tool does not do
This estimator reflects historical patterns in aggregate UK appeal data; it cannot account for case-specific facts, the skill of your legal team, or changes in judicial interpretation. A 20% historical reversal rate does not mean your case has a one-in-five chance — it means cases like yours, in the past, succeeded about one time in five.
Use this tool to set realistic expectations and understand which factors historically improve appeal outcomes. For actual case strategy, speak to a solicitor experienced in criminal appeals or contact the Criminal Cases Review Commission.
Common questions
What percentage of criminal appeals succeed in the UK?
Overall success rates vary widely by conviction type: summary convictions see reversal in roughly 25–35% of appeals, while Crown Court convictions (indictable offences) have a lower rate around 15–20%. Fresh evidence appeals have historically performed better, with success rates approaching 30–40% when new material is substantive and admissible.
Does the time since trial affect appeal chances?
Yes, substantially. Appeals lodged within the first year after conviction succeed more often because procedural grounds and trial errors are easier to demonstrate with a fresh record. Beyond five years, appeals rely almost entirely on new evidence or a change in law, and historical data shows success rates drop by half or more compared to immediate appeals.
What counts as 'new evidence' for appeal purposes?
New evidence must be credible, relevant, and not reasonably available at the original trial. DNA and forensic re-analysis meet this standard most reliably; witness recantations are scrutinised heavily for credibility. Expert reinterpretation of existing evidence is treated as weaker unless it reveals a clear error or advances in the field have made the original testimony demonstrably wrong.