Who prosecutes election-related criminal offences?

Election Dispute SettlementRules and Regulations of the Kingdom of Bhutan, 2013

11. Investigation Committee

11.1 The CEDSB/DEDSB shall,whenever necessary, appoint an Investigation Committee

...

12. Investigation

12.1 TheInvestigation Committee shall, on the instruction of the Election DisputeSettlement Bodies carry out the preliminary investigation of the case.

12.2 The InvestigationCommittee shall investigate and establish the facts for decision of the CEDSB/DEDSB.

Source:

http://www.election-bhutan.org.bt/wp-content/uploads/2013/04/ElectionDisputeSettlementRules.pdf