Reasonable Doubt

For writers taught to write formally

AI detectors give one verdict. This shows you where they disagree, before anyone accuses you.

AI detectors can misread careful, formal writing as machine-written. In our tests, a commercial detector flagged 13% of real student essays written before ChatGPT existed, and 60% of human-written scientific abstracts. A single score can't tell you which kind of mistake you're looking at.

This tool doesn't hand you one more score to argue about. Paste in a piece of text and it runs through several independent detectors — a fine-tuned classifier, statistical detectors, and a commercial detector (Sapling) — at once, and shows you exactly where they agree and where they don't.

Detector results are probabilistic signals, not proof of AI use or human authorship. This tool is not a substitute for an institution's own academic-integrity process.

Same paragraph, different detectors, different answers

  • RoBERTa classifierHuman
  • Log-perplexity detectorAI-generated
  • GPTZeroUnavailable

Illustrative example — not a live result.

Run the scan

Paste in a paragraph or two. It runs through every detector we have wired up and shows you exactly where they land.

What we found

Preliminary results, November 2026. Not peer-reviewed.

  • A commercial detector (Sapling) flagged 13% of 170 genuine student essays written before ChatGPT existed. Our own fine-tuned classifier flagged 18%.
  • In a pre-registered test, Sapling flagged 36 of 60 human-written scientific abstracts from before 2020 (60%) as AI-generated, compared with 12% of student essays. Text length didn't explain it: student essays cut to abstract length were flagged 8% of the time. The other three detectors flagged almost none of the abstracts.
  • Detection depended heavily on which AI wrote the text. Two free statistical detectors caught 70-93% of GPT-written text but 5% or less of Gemini-written text.
  • We expected non-native English writers to be flagged more often. Across two studies the difference leaned that way but was not statistically reliable at our sample size.

Human essays: Write & Improve corpus and LOCNESS (Centre for English Corpus Linguistics, UCLouvain), via BEA-2019. Abstracts: arXiv (public domain).