Etterforsker1 Gruppen AS is a detective agency located in Sandefjord, Norway. It was established in 2014.

Etterforsker1 was established by Thomas Mathiesen in 2014 and is located in Sandefjord.^[1][2][3] Before starting Etterforsker1 Mathiesen worked in information technology in the Netherlands.^[4]

Etterforsker1 employs 13 investigators and since it's founding revenues have quadrupled to NOK 2.2 million.^[2][3][4]

Etterforsker1's range of operations includes investigations of spousal infidelity, finding missing persons and data recovery and mobile phones.

Infidelity investigations comprise 70% of cases handled, locating mission persons accounts for 30% and data recovery cases take up 15% of the caseload.

The firm also investigates wrongful convictions and has contract with vendors in the Netherlands for DNA, fingerprint and writing analysis services.^[4]

The company's tax list lookup service has raised questions regarding its legality.

According to policy, searching for people on the tax list is logged and disclosed.

For a fee Etterforsker1 will perform the search allowing the requestor to maintain their anonyminity.

The Norwegian Data Inspectorate stated that third-party searches of the tax list are not prohibited.^[5][6]