Integrity of digital evidence is under an imminent quantum threat. Adversaries are mounting “harvest-now, decrypt-later” attacks, harvesting encrypted evidence today for decryption later using cryptographically relevant quantum computers forecast to materialize within 8–15 years. Yet, postquantum cryptography adoption has hardly scratched the surface in the digital forensics community, a critical vulnerability window. This work presents a holistic framework for QEDEPC: an integrated framework that combines NIST-standardized postquantum cryptography, blockchain-automated chain-of-custody, multi-modal AI classification with explainability, and quantum key distribution simulation. We have implemented CRYSTALSDilithium3 and KYBER512 via liboqs for quantum-resistant signatures and key encapsulation, Hyperledger Fabric smart contracts for ISO/IEC 27037 and Section 65B IT Act compliance, and containerized YOLOv8, RoBERTa, and LSTM models for AI-assisted artifact triage with SHAP explainability. Component validation on commodity hardware demonstrates: (1) cryptographic correctness via NIST test vectors, (2) blockchain immutability against tampering, (3) AI pipeline functionality with generated explanations, and (4) integration of the end-to-end workflow. QEDEPC is the first framework that simultaneously achieves post quantum cryptographic resilience, tamper proof blockchain chain-of-custody with legal compliance mapping, explainable AI-driven classification, and production grade deployment. The code is open sourced, while Docker containerization has been used. Index Terms—Post-quantum cryptography, digital forensics, CRYSTALS-Dilithium, CRYSTALS-KYBER, blockchain, smart contracts, chain-of-custody, artificial intelligence, quantum key distribution, evidence preservation, quantum computing threat, cryptographic agility, NIST standards, explainable AI