Short answer: No Jain shastra states that Krishna is in Narak. In Jainism, Krishna is not recognized as a Tirthankar or as an authoritative figure within the Jain scriptures. If you’ve heard this claim, it likely comes from non‑Jain Hindu texts, not from Jain canonical literature.

Notes:

• Jain texts focus on the 24 Tirthankaras and the path to moksha; they do not place Krishna in Narak as a doctrinal statement.
• Different Jain sects (Digambar and Svetambar) may have varying attitudes toward Krishna as a historical/religious figure outside Jain doctrine, but neither sect presents a Jain shastra asserting Krishna’s presence in Narak.

If you’d like, I can explain how Jainism views Krishna in relation to Hindu traditions, or point you to Jain sources that discuss Krishna from a Jain perspective.