diff --git a/prisma/migrations/20260621135734_add_case_model/migration.sql b/prisma/migrations/20260621135734_add_case_model/migration.sql
new file mode 100644
index 0000000..8c590fc
--- /dev/null
+++ b/prisma/migrations/20260621135734_add_case_model/migration.sql
@@ -0,0 +1,18 @@
+-- CreateTable "cases"
+CREATE TABLE "cases" (
+    "id" TEXT NOT NULL PRIMARY KEY,
+    "title" TEXT NOT NULL,
+    "ownerId" TEXT NOT NULL,
+    "status" TEXT NOT NULL DEFAULT 'open',
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "updatedAt" TIMESTAMP(3) NOT NULL
+);
+
+-- CreateIndex
+CREATE INDEX "cases_ownerId_idx" ON "cases"("ownerId");
+
+-- AddForeignKey for cases
+ALTER TABLE "cases" ADD CONSTRAINT "cases_ownerId_fkey" FOREIGN KEY ("ownerId") REFERENCES "users"("id") ON DELETE RESTRICT ON UPDATE CASCADE;
+
+-- AddForeignKey for investigation_notes
+ALTER TABLE "investigation_notes" ADD CONSTRAINT "investigation_notes_caseId_fkey" FOREIGN KEY ("caseId") REFERENCES "cases"("id") ON DELETE CASCADE ON UPDATE CASCADE;
diff --git a/prisma/migrations/migration_lock.toml b/prisma/migrations/migration_lock.toml
new file mode 100644
index 0000000..564d8c6
--- /dev/null
+++ b/prisma/migrations/migration_lock.toml
@@ -0,0 +1,3 @@
+# Please do not edit this file manually
+# It should be added to your version control system (i.e. Git)
+provider = "postgresql"
diff --git a/prisma/schema.prisma b/prisma/schema.prisma
index bbb931c..985264e 100644
--- a/prisma/schema.prisma
+++ b/prisma/schema.prisma
@@ -14,6 +14,7 @@ model User {
   watchlist Watchlist[]
   notificationPreferences NotificationPreference[]
   auditLogs               AuditLog[]
+  cases                   Case[]
 
   @@map("users")
 }
@@ -116,6 +117,25 @@ model GovernanceEvent {
   @@map("governance_events")
 }
 
+// ---------------------------------------------------------------------------
+// Case Management – independent investigation tracking
+// ---------------------------------------------------------------------------
+
+model Case {
+  id        String   @id @default(cuid())
+  title     String
+  ownerId   String
+  status    String   @default("open") // "open", "in_progress", "closed", "on_hold"
+  createdAt DateTime @default(now())
+  updatedAt DateTime @updatedAt
+
+  owner                User                  @relation(fields: [ownerId], references: [id])
+  investigationNotes   InvestigationNote[]
+
+  @@index([ownerId])
+  @@map("cases")
+}
+
 // ---------------------------------------------------------------------------
 // Investigation Notes – issue #127
 // ---------------------------------------------------------------------------
@@ -133,7 +153,8 @@ model InvestigationNote {
   createdAt  DateTime @default(now())
   updatedAt  DateTime @updatedAt
 
-  auditEntries NoteAuditLog[]
+  case          Case            @relation(fields: [caseId], references: [id], onDelete: Cascade)
+  auditEntries  NoteAuditLog[]
 
   @@index([caseId])
   @@map("investigation_notes")