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
# 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
Courts and Jurisdictions
# 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
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:
# Bulk data available at:
# https://case.law/bulk/download/
# Formats: JSON (full case data) or text-only
# Organized by jurisdiction and reporter
Key Jurisdictions
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