Double signing is the only penalized validator fault in KIRA. Double signing refers to a situation where validator proposes or participates in the production of two different blocks at the same block height. In short double-signing means creating or attempting to create a fork - that is publishing two parallel versions of the blockchain state. Forks can mischeave network observers because they allow the attacker to spend the same funds multiple times - once from each fork. To prevent such situation from occurring KIRA permanently jails validators who double signed.

Double signing does NOT necessary means that the validator is malicious on purpose and there can be many possible reasons for the node operator to unintentionally misbehave:

Majority of double-signing events occurs unintentionally and for that reason KIRA does NOT automatically slash delegators stake without governance judgement and does NOT automatically punish validators in any other way then by removing them from consensus. The reason this is possible is that validator set is governance permissioned and potentially malicious nodes can't re-join the validator set again by simply creating a new node with a new key and moving coins, as in the case of other PoS chains. The governance of the network is tasked with deciding fate of all validator nodes that commit double signing fault, weather they should be unjailed, left permanently removed from the validator set or slashed in critical cases of coordinated attacks. In either case the governance protects staked funds of delegators thus almost entirely preventing risk of accidental loss of funds.

Besides having ability to unjail validators who commited double signing, governance can define UnjailMaxTime network property, which defines time within which proposal to unjail validator must be submitted. If unjail proposal is not submitted then node becomes permanently jailed AKA tombstoned.