Criminal investigation offers a clearly defined measure of success? what is this measure?

"Arresting a suspect" is that measure.

The captured suspect in a criminal examination waiting in care for cross examination has bounty to consider. Indeed, even the most experienced criminals will be worried about how much confirmation the police have for demonstrating their association with the wrongdoing. Thus if a suspect is arrested during criminal investigation it offers a clearly defined measure of success.

I believe the answer is: Arresting a suspect
In law enforcement agencies, someone that has the highest status among other members are the one that manage to arrest more target of investigation. The number of arrest measure both ability to connect evidences, analyzing skills, and correct usage of resources which contribute to the overall credibility of an investigator.

The correct answer is "  it was believed that the dispute emerged in 632 just after the death of the prophet muhammad."