caselaw-access-api

# Caselaw Access Project API ## Overview The Caselaw Access Project (CAP) by Harvard Law School provides free access to 6.9 million US court opinions spanning 360+ years. The REST API enables searching, filtering, and downloading full-text case opinions from all federal and state courts. No authentication required for metadata; API key (free registration) required for full text of post-1923 cases. ## API Endpoints ### Base URL ``` https://api.case.law/v1/ ``` ### Cases ```bash # Search cases by keyword curl "https://api.case.law/v1/cases/?search=free+speech&decision_date_min=2020-01-01" # Get a specific case by ID curl "https://api.case.law/v1/cases/12345678/" # Filter by jurisdiction and court curl "https://api.case.law/v1/cases/?jurisdiction=us&court=us-sup-ct&search=miranda+rights" # Filter by date range curl "https://api.case.law/v1/cases/?decision_date_min=2015-01-01&decision_date_max=2025-12-31" # Get full text (requires API key for post-1923) curl -H "Authorization: Token YOUR_API_KEY" \ "https://api.case.law/v1/cases/12345678/?full_case=true" ``` ### Query Parameters | Parameter | Description | Example | |-----------|-------------|---------| | `search` | Full-text search | `search=due+process` | | `jurisdiction` | Filter by jurisdiction slug | `jurisdiction=cal` (California) | | `court` | Filter by court slug | `court=us-sup-ct` | | `decision_date_min` | Earliest date | `decision_date_min=2020-01-01` | | `decision_date_max` | Latest date | `decision_date_max=2025-12-31` | | `cite` | Search by citation | `cite=410+U.S.+113` | | `name_abbreviation` | Case name | `name_abbreviation=Roe+v.+Wade` | | `ordering` | Sort results | `ordering=-decision_date` | | `page_size` | Results per page (max 100) | `page_size=50` | | `full_case` | Include full text | `full_case=true` | ### Courts and Jurisdictions ```bash # List all courts curl "https://api.case.law/v1/courts/" # List all jurisdictions curl "https://api.case.law/v1/jurisdictions/" # List all reporters (case report series) curl "https://api.case.law/v1/reporters/" ``` ## Python Usage ```python import requests BASE_URL = "https://api.case.law/v1" def search_cases(query: str, jurisdiction: str = None, court: str = None, max_results: int = 20) -> list: """Search US case law.""" params = {"search": query, "page_size": min(max_results, 100)} if jurisdiction: params["jurisdiction"] = jurisdiction if court: params["court"] = court resp = requests.get(f"{BASE_URL}/cases/", params=params) resp.raise_for_status() data = resp.json() cases = [] for case in data.get("results", []): cases.append({ "id": case["id"], "name": case["name_abbreviation"], "citation": case["citations"][0]["cite"] if case.get("citations") else None, "court": case["court"]["name"], "date": case["decision_date"], "url": case["frontend_url"] }) return cases # Search Supreme Court cases results = search_cases("fourth amendment", court="us-sup-ct") for case in results: print(f"{case['citation']}: {case['name']} ({case['date']})") ``` ## Bulk Data Access For large-scale research, download bulk datasets instead of querying the API: ```bash # Bulk data available at: # https://case.law/bulk/download/ # Formats: JSON (full case data) or text-only # Organized by jurisdiction and reporter ``` ## Key Jurisdictions | Slug | Jurisdiction | Cases | |------|-------------|-------| | `us` | Federal (all) | ~1.5M | | `us-sup-ct` | US Supreme Court | ~65K | | `cal` | California | ~500K | | `ny` | New York | ~600K | | `tex` | Texas | ~300K | | `ill` | Illinois | ~250K | ## Authentication ``` 1. Register at https://case.law/user/register/ 2. Get API token from your account page 3. Include in requests: Authorization: Token YOUR_TOKEN ``` Free accounts get full text for pre-1923 cases. Post-1923 full text requires an API token (still free). ## References - [CAP API Documentation](https://case.law/api/) - [CAP Bulk Data](https://case.law/bulk/download/) - [Harvard Library Innovation Lab](https://lil.law.harvard.edu/)