The 2026 PI SERP Authority Report: An 11-Question Structural Audit of 1,005 US Personal Injury Law Firm Websites Against the Personal Injury Organic Authority Engine (PIOAE) Framework

Personal injury (PI) is the highest-CPC legal vertical in United States search: commercial-intent queries clear USD 100 to 300 per click and cost per signed case from paid channels regularly exceeds USD 5,000. In this environment, the practical question for a managing partner evaluating an SEO program is not whether the firm ranks, Google Page 1 alone is table stakes, but whether the site is structurally engineered to compound authority over time. This study operationalizes that question as an eleven-item rubric drawn from the Personal Injury Organic Authority Engine (PIOAE) framework and applies it externally to a rank-controlled sample of 1,005 unique PI law firm websites ranking on the first page of Google Search for five practice-area keywords across 51 US metropolitan markets. For every firm we assembled independent third-party authority, traffic, keyword-ranking, backlink, and AI-visibility signals from established SEO-data providers; ran an industry-standard mobile-performance audit; crawled each firm's sitemap, attorney bios, informational pages, contact forms, and mobile viewport; and classified 5,984 unique referring domains with a large-language-model judge. Each firm was graded across four pillars (Technical Stability, Intent Capture, Authority Reinforcement, Case Acquisition Optimization) on an eleven-question rubric with a maximum score of 11. We find that zero firms of 1,005 reach the Authority Built band (10-11/11), only 5 firms reach Authority Leaking (7-9/11), 337 firms are Authority Underbuilt (4-6/11), and 663 firms, 66.0% of the sample, are Authority Absent (0-3/11). The median firm's homepage takes 5.5 seconds to reach the Largest Contentful Paint on a mid-range mobile device, 3.7x the framework's 1.5-second threshold. Only 1.5% pass the mobile-render check, only 3.1% deploy a YMYL-aware intake form, and only 3.2% of firms have topically-relevant backlink profiles. The rubric's total score correlates strongly with organic traffic (Spearman ρ = 0.55) and Domain Authority Score (ρ = 0.55), confirming that the framework measures a real structural phenomenon, but only weakly with AI-answer visibility (ρ = 0.19), suggesting that classical structural authority and AI-answer citation are partly decoupled surfaces. We anchor the findings to Google's published patents on knowledge graphs and factual-entity content, discuss three surprising findings (mobile render as a vertical-wide structural crisis, function-first mobile layouts as newly table-stakes, and the AI-visibility decoupling), and offer prioritized recommendations for firms.