# Identity Collision **Entity class:** Entity-resolution failure mode **Domains:** Identity systems / screening / record linkage / security ## Definition An **identity collision** occurs when a system treats two different people as possible instances of the same identity because their selectors overlap. The encountered person may share a name, date of birth, transliteration, document feature, biometric similarity, address, account, device, or other attribute with the person represented by the risk record. In watchlist screening, the collision case is specific: the encountered person is **not listed**, but is provisionally matched to somebody who is. GAO defines watchlist misidentification as a person initially matched to a watchlist name who is found, after closer examination, not to match any watchlist record. Identity collision is the precision cost of broad matching. Strict rules reduce collisions but miss aliases, spelling variants, incomplete records, and evasion attempts. Broader rules increase recall and the number of innocent people requiring resolution. The design problem is therefore how quickly and harmlessly the system can move from **possible match** to **negative identity resolution**. When unresolved collision results are distributed, the collision becomes a [[wiki/Distributed Erroneous State|Distributed Erroneous State]]. When later observations attach to that fused record, it becomes [[wiki/Identity-Rooted Error Amplification|Identity-Rooted Error Amplification]]. ## Relationships - **watchlist case:** [[wiki/Watchlist Misidentification|Watchlist Misidentification]]. - **distinct failure:** [[wiki/Erroneous Watchlist Inclusion|Erroneous Watchlist Inclusion]]. - **technical layer:** [[wiki/Entity Resolution|Entity Resolution]], [[wiki/Identity Fusion|Identity Fusion]], [[wiki/False Match|False Match]], and [[wiki/Probabilistic Record Linkage|Probabilistic Record Linkage]]. - **remedy:** [[wiki/Negative Identity Assertion|Negative Identity Assertion]] and [[wiki/Watchlist Redress|Watchlist Redress]]. - **master harm map:** [[wiki/Security Harms Topology|Security Harms Topology]]. - **analysis:** [[research/Harms Incurred While Bringing Preventive Systems Online|Harms Incurred While Bringing Preventive Systems Online]]. ## Sources / Provenance - [GAO-06-1031 — Terrorist Watch List Screening](https://www.gao.gov/assets/gao-06-1031.pdf) (2006-09-29). - [GAO-09-292 — Secure Flight Matching Performance](https://www.gao.gov/assets/a289639.html) (2009-05-13). - [GAO-25-108349 — Terrorist Watchlist Nomination and Redress](https://www.gao.gov/products/gao-25-108349) (2025-08-14). **As of:** 2026-09-23