Here is the full list of all 22 DETECTIVE - there are Stella Porta Case achievements worth 1,000 gamerscore.
Welcome detective.
Arrive at the crime scene.
Find the first corpse.
Find the fake police badge.
Find the first Stella Porta contract.
Arrive at the police station.
Reach the second crime scene.
Ask your neighbour.
Find the medical prescription.
Find Alex's corpse.
Return to the police station again.
Arrive at third crime scene.
Read the extremist forum.
Find the broken fence.
Find the dirty boots.
Arrive at the office for the third time.
Reach the coordinates.
Find the cultist's lair.
Read the cultist's laptop.
Use the door lever.
Discover the portal.
Cross the portal.