10 Common Mistakes in Forensic Psychological Report Writing — and How Cross-Examiners Probe Them

The ten most common mistakes, ranked by frequency.

Grisso (2010) analyzed 62 forensic reports and ranked the faults by how many reports contained each one. In descending order of frequency:

1. Opinions without sufficient explanations — 56% of reports
2. Forensic purpose unclear — 53%
3. Organization problems — 36%
4. Irrelevant data or opinions — 31%
5. Failure to consider alternative hypotheses — 30%
6. Inadequate data — 28%
7. Data and interpretation mixed — 26%
8. Over-reliance on a single source of data — 22%
9. Language problems — 19%
10. Improper test uses — 15%

All ten categories and percentages are from Grisso, T. (2010), “Guidance for improving forensic reports: A review of common errors,” Open Access Journal of Forensic Psychology, 2, 102–115 (full text). We originally explored this study on our blog; this page is the practitioner version — each mistake paired with the cross-examination pattern it invites.

Where the numbers come from — and why they sting.

Grisso reviewed 62 forensic reports drawn from 36 candidates for board certification with the American Board of Forensic Psychology whose practice samples were not approved by ABFP reviewers. He identified 30 discrete faults across the sample and ranked the ten most frequent. These were not student papers. They were work samples from practicing, doctoral-level psychologists who considered the reports strong enough to submit for board review.

In our own review work, we see the same ten categories recur in reports today — an observation, not a research finding, but one the peer-reviewed literature is consistent with. A 2018 article in Psychiatry, Psychology and Law described these same faults as “recurring problems,” noted that similar faults had been identified in earlier studies, and proposed a writing checklist to address them (Zwartz, 2018, full text). The categories below are stable enough that opposing counsel can prepare for them in advance. So can you.

Each mistake, and the question it invites on cross.

For each category: what Grisso documented, how it surfaces under cross-examination, and what to consider before finalizing. The attorney’s questions below are illustrative patterns, not quotations from any transcript.

1. Opinions without sufficient explanations (56%)

The most frequent fault in the sample: the report states a conclusion but never shows the reasoning that connects the data to it. The opinion may be entirely sound — the report just doesn’t demonstrate why.

Under cross-examination, this is the gap behind the classic invitation: “Doctor, walk the jury through how you got from this test score to that conclusion.” If the reasoning chain lives only in your head, you are reconstructing it live, under pressure, in front of the fact-finder. Consider giving every opinion an explicit because-chain in the report itself: the data, the inference, and the reasoning that links them, so your testimony walks through what is already on the page.

2. Forensic purpose unclear (53%)

More than half of the reports failed to make clear what legal question they were answering — the referral question, the legal standard, or both.

The cross-examination version: “Doctor, what question were you retained to answer? Can you show the jury where your report states it?” A report that cannot point to its own purpose invites the suggestion that the evaluation drifted — or answered a question nobody asked. Consider stating the referral question and the controlling legal standard on the first page, and scoping every opinion section back to it.

3. Organization problems (36%)

Data scattered across sections, findings separated from the opinions they support, no discernible path from information to conclusion.

A disorganized report hands the cross-examiner the sequence: “On page 4 you note the evaluee’s account. On page 12 you reach your conclusion. Where is the section that connects them?” Reading passages out of order in front of a jury makes even sound reasoning look improvised. Consider a structure that moves visibly from data to reasoning to opinion, so any passage an attorney reads aloud sits inside an obvious logical frame.

4. Irrelevant data or opinions (31%)

Material that serves no forensic purpose: history unrelated to the referral question, gratuitous clinical detail, opinions beyond the scope of the retention.

Every irrelevant paragraph is surface area you must defend: “Doctor, what does this detail have to do with the question the court asked you?” Worse, irrelevant content can open lines of questioning the evaluation was never designed to support. Consider a relevance pass before signing — for each paragraph, ask what referral question it serves, and cut what has no answer.

5. Failure to consider alternative hypotheses (30%)

The report presents one explanation for the findings without documenting that rival explanations were considered and why they were set aside.

This is among the most predictable lines of scrutiny in expert testimony: “Doctor, did you consider whether [the alternative] explains these findings? Where in your report is that analysis?” An answer of “I considered it but didn’t write it down” is far weaker than a paragraph that already names the rival hypothesis and the data that ruled it out. Consider documenting the alternatives you weighed — the act of writing them down is itself a check on confirmation bias.

6. Inadequate data (28%)

Opinions resting on thinner data than the conclusions require: missing records, uncontacted collaterals, single interviews carrying multi-part opinions.

Cross-examination finds the gap by inventory: “You formed this opinion without reviewing the treatment records, correct? You never spoke with the evaluee’s employer, correct?” Each “correct” accumulates. Consider a data-sufficiency audit against each opinion — and where a source was genuinely unavailable, say so in the report and describe how the limitation affects the confidence of the opinion.

7. Data and interpretation mixed (26%)

Observation and inference blended in the same sentence — “the evaluee was evasive” presented as if it were a fact rather than an interpretation of behavior.

The probe is short and effective: “Doctor, is that something you observed, or your interpretation of what you observed?” Once one blended sentence is exposed, every descriptive sentence in the report becomes fair game for the same question. Consider keeping observation and inference structurally separate — what was seen and heard in one register, what it means in another, with the inferential step marked.

8. Over-reliance on a single source of data (22%)

Opinions anchored on one source — most often the evaluee’s self-report — without corroboration from records, collateral interviews, or testing.

The pattern on cross: “So this opinion rests entirely on what the evaluee told you — a person with an interest in the outcome of this case?” Consider triangulating every load-bearing fact across at least two independent sources where possible, and where an opinion genuinely rests on a single source, acknowledging that explicitly and calibrating the strength of the opinion to match.

9. Language problems (19%)

Undefined jargon, pejorative phrasing, or advocacy-flavored language that reads as taking a side rather than analyzing a question.

The cross-examination move is simply to read the sentence aloud and ask you to defend it: “Doctor, you wrote that the evaluee ‘manipulated’ the staff. Tell the jury what you meant by that word.” Every loaded word is a question you will eventually answer in front of a fact-finder. Consider a language pass for terms a non-clinician cannot parse and for words that carry a charge the data don’t — plain, neutral, defined.

10. Improper test uses (15%)

Instruments used outside their validation: wrong population, wrong purpose, clinical instruments carried into forensic questions they were never validated to answer.

This is where report-writing error meets admissibility exposure: “Doctor, is this instrument validated for this population, in this forensic context, for this question?” Under Federal Rule of Evidence 702 as amended in December 2023, the reliability of the method as applied is a question for the court, not just the jury. Consider verifying, for each instrument, the population match, the currency of the norms, and the forensic (not merely clinical) validation — and documenting that reasoning in the report.

Turn the list into a pre-signature routine.

The ten categories above are stable, published, and known to the attorneys who will read your report. That makes them auditable before you sign. Our Daubert self-audit checklist covers the methodology, instrument, and application questions (mistakes 1, 5, 6, 8, and 10 map directly onto it), and the cross-examination prep template works the same ground from the testimony side. If you already keep a personal checklist, see how manual checklists and structured review divide the work.

ForensicShield’s report review covers the same territory as this list: it examines a draft report for unexplained opinions, unclear forensic purpose, unaddressed alternative hypotheses, data-sufficiency gaps, observation/inference blending, single-source anchoring, language vulnerabilities, and instrument fit — calibrated to the evaluation type and to the admissibility framework of the controlling jurisdiction, across all 55 US jurisdictions. Findings are framed for your consideration; the psychologist remains the expert, the author, and the signatory. Every legal citation the review surfaces passes through a verification pipeline against public court databases and carries a verification status badge; verified citations link directly to the opinion. The review runs HIPAA compliant, with a BAA, AES-256 encryption, and AI inference inside a HIPAA-eligible AWS Bedrock boundary — PHI never leaves it. See how the review applies to specific evaluation types and specific jurisdictions.

Common questions.

What is the most common mistake in forensic psychological report writing?

Opinions stated without sufficient explanation. In Grisso’s 2010 review of 62 forensic reports, 56% contained conclusions whose reasoning was not demonstrated in the report — the single most frequent fault, ahead of unclear forensic purpose (53%).

Are Grisso’s 2010 findings still relevant in 2026?

The study has not been replicated at the same scale, so treat persistence as informed observation rather than settled research. That said, a 2018 peer-reviewed article described the same faults as recurring problems and noted similar findings in earlier studies, and in our own review work the same ten categories appear in current reports. The categories describe structural features of report writing, not passing trends.

How do I check my own report for these mistakes before signing?

Run a deliberate pre-signature audit rather than a re-read: verify each opinion has a documented reasoning chain, the referral question is stated and answered, alternatives are documented, data sufficiency matches each conclusion, observation and inference are separated, and every instrument is validated for its use. Our free Daubert self-audit checklist structures that pass; ForensicShield automates the same kind of review on any report you upload.

Can one of these mistakes get a report excluded from evidence?

Usually they affect weight and credibility rather than admissibility on their own. But the categories that touch methodology — improper test use, inadequate data, and unexplained inferential leaps — go to reliability under Federal Rule of Evidence 702, and the December 2023 amendment requires the proponent to demonstrate reliability to the court before the jury hears the testimony. This page is informational and is not legal advice; standards vary by jurisdiction.

Authority behind the list.

• Grisso, T. (2010). Guidance for improving forensic reports: A review of common errors. Open Access Journal of Forensic Psychology, 2, 102–115. Full text via UMass Chan eScholarship. Source of all ten error categories and percentages on this page.
• Zwartz, M. (2018). Report writing in the forensic context: Recurring problems and the use of a checklist to address them. Psychiatry, Psychology and Law, 25(4), 578–588. Full text via PubMed Central. Peer-reviewed discussion of the same faults as recurring problems.
• Federal Rule of Evidence 702, as amended December 1, 2023 — the reliability gate the methodology-related mistakes implicate.

The cross-examination patterns on this page are illustrative preparation prompts drawn from our review practice, not quotations from transcripts or from the cited studies. This page is informational and does not constitute legal advice.