[citation needed] After World War II, Croiset was sometimes consulted by Dutch police authorities for cases involving missing persons, or murder.

He gained a reputation as a reliable consultant in the area of missing persons, and his fame extended beyond the Netherlands, as anecdotes about his abilities came to be discussed in other countries.

Although police were skeptical, his expenses were paid by the wealthy property tycoon Con Polites, who was interested in the case, and publicity was such that Croiset's ideas were thought to be worthy of consideration.

In 1978, the Chief Constable of Devon and Cornwall Police hired Croiset to investigate the disappearance of Genette Tate, but he provided no information of value.

[6][7] The skeptic James Lett has written: The truth is that the overwhelming majority of Croiset’s predictions were either vague and nonfalsifiable or simply wrong.

[8][9]The Dutch parapsychologist Wilhelm Tenhaeff [nl] has written Croiset had genuine psychic powers due to the information he had given in police cases.