Highprince of Information
The Highprince of Information has authority over criminal investigations, particularly those of interest to the Crown. The title also grants permission to enter another highprince's land and question their servants and troops. Denying the Highprince of Information access to these could be taken as denying the kings will.
As Torol Sadeas suggested, King Elhokar made him Highprince of Information. His first task was the investigation of a suspected assassination attempt on the king during a chasmfiend hunt, but Sadeas disproved that assertion later. Sadeas renounced the title of Highprince of Information later, in order to distance himself from the king's authority and antagonize the throne and Dalinar, as it had been his idea to institute these functions into Elhokar's kingdom as a means of preparing the other Highprinces for his nomination as Highprince of War. After the relocation to Urithiru and Sadeas' murder, Highprince Aladar was named Highprince of Information by Dalinar. As it was not in Dalinar's own authority to do so, it can be surmised that either Elhokar ratified this decision after the fact or that he gave his uncle the authority to make this nomination in his name beforehand.