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21 September 2026
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Probabilistic Legal Reasoning

Exploring how probabilistic AI and formal legal logic can work together to make complex legal reasoning explainable.

Ciaran McGonagleVideo

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About the Project

This is an experimental application exploring how probabilistic AI can be incorporated into formal legal reasoning.

One of the challenges in making law computable is the recursive nature of legal definitions. A legal concept depends on another definition, which depends on another, until eventually reaching a proposition that requires subjective interpretation or an assessment of incomplete evidence.

The application explores whether probabilistic AI can help evaluate these propositions within an explicitly defined hierarchy of legal rules.

For this proof of concept, I used a selection of the definitions underpinning Article 88F of the UK's new cryptoasset regulatory framework, which establishes the definition of a qualifying cryptoasset.

The application takes the Bitcoin whitepaper, uses TypeSafe AI's Jev model to evaluate individual factual and interpretative propositions, and presents the resulting probabilities within the underlying legal hierarchy. An LLM then generates a narrative explaining the assessment and identifying unresolved questions.

The initial results illustrate both the potential and the limitations of this approach.

Jev produced assessments consistent with the whitepaper for relatively straightforward factual propositions, including cryptographic security, digital representation and electronic transferability.

However, its assessment of fungibility returned a probability of 52%. Fungibility is not explicitly defined in the whitepaper, and its legal characterisation requires consideration of the relevant regulatory framework and guidance.

This highlights the importance of domain specification and standardised representations of contracts and legislation.

The longer-term objective is to explore how probabilistic assessments can be confined to specific questions within a broader framework of formal legal logic, preserving the relationships between legal concepts and making uncertainty visible.

Practice Areas

Key Features

Recursive legal reasoning: Represents legal definitions as a hierarchy of interconnected concepts and logical conditions. Probabilistic assessment: Uses TypeSafe AI's Jev model to evaluate individual factual and interpretative propositions. Document analysis: Accepts a token whitepaper and evaluates its contents against selected regulatory definitions. Explainable assessment: Displays individual probabilities alongside their associated legal concepts and supporting evidence. Uncertainty identification: Highlights propositions requiring additional evidence or subjective legal interpretation. AI-generated legal analysis: Produces a narrative explaining the probabilistic findings, relevant legal conditions and unresolved questions. Domain-specific legal framework: Uses a structured representation of selected Article 88F requirements.

About the Creator

CM
Ciaran McGonagle