How to investigate corruption?

These days, a corruption case is going before Norwegian courtrooms. A former top official in an international sports federation has been charged with receiving bribes in the form of gifts and services. I myself have worked for several years investigating corruption cases in private businesses when I worked in a "big four" company, and have gained the following experiences:

The investigation process often starts with an anonymous tip, alert or red flags related to suspicious transactions. In connection with this, an internal investigation is often carried out before the matter is eventually reported to the police/Økokrim. An investigation process consists of mapping the facts and assessments of this. Mapping the facts consists, among other things, of: get an overview of the people and organizations involved (internal and external) clarify relationships between the parties involved (is there any acquaintance, kinship or common financial interests between them?) chart financial transactions between the partners recreate a sequence of events (timeline) The method for mapping the facts mainly consists of data analysis and interviews of those involved and other people in and around the business. The purpose is to get an overview of the parts mentioned above. If there is a suspicion that a supplier or customer has obtained a disproportionately favorable agreement with a company, facts will be collected about the agreement that has been concluded, who has negotiated the agreement, clarify any relationships between those involved, physical transactions linked to the agreement, current internal procedures linked to such agreements (e.g. who must approve such agreements, payment terms, discount matrices, etc.). Data sources will then be interviews, review of agreements, invoices and payments, collection of information from public registers (Brønnøysund). After an investigation team has formed a good picture of the facts, assessments are made relating to whether there is reasonable reason to suspect corruption and what, if any, should be done in relation to this.