There is a total of 241 clues in the game. You should unlock the trophy when ou've got 228 clues found in your stats (but in my sats it was 238, i don't know why).
I add a link for each case, just follow the walktrought, it is really complete.
Or you can use the video guide in the trophy Patrol : 11Upon Reflection - 4 - http://lanoire.wikia.com/wiki/Upon_Reflection
Buyer Beware -7 -
http://lanoire.wikia.com/wiki/Buyer_BewareTraffic desk : 41The Driver's Seat - 14 - http://lanoire.wikia.com/wiki/The_Driver%27s_Seat
A Marriage Made In Heaven - 9 - http://lanoire.wikia.com/wiki/A_Marriage_Made_in_Heaven
The Fallen Idol - 18 -
http://lanoire.wikia.com/wiki/The_Fallen_IdolHomicide desk : 96The Red Lipstick Murder - 19 - http://lanoire.wikia.com/wiki/The_Red_Lipstick_Murder
The Golden Butterfly - 12 - http://lanoire.wikia.com/wiki/The_Golden_Butterfly
The Silk Stock Murder - 17 - http://lanoire.wikia.com/wiki/The_Silk_Stocking_Murder
The White Shoe Slaying - 17 - http://lanoire.wikia.com/wiki/The_White_Shoe_Slaying
The Studio Secretary Murder - 17 - http://lanoire.wikia.com/wiki/The_Studio_Secretary_Murder
The Quarter Moons Murder - 14 -
http://lanoire.wikia.com/wiki/The_Quarter_Moon_MurdersVice desk : 39The Black Caesar - 13 - http://lanoire.wikia.com/wiki/The_Black_Caesar
The Set Up - 11 - http://lanoire.wikia.com/wiki/The_Set_Up
Manifest Destiny - 15 -
http://lanoire.wikia.com/wiki/Manifest_DestinyArson desk : 54The Gas Man - 16 - http://lanoire.wikia.com/wiki/The_Gas_Man
A Walk In Elysian Fields - 13 - http://lanoire.wikia.com/wiki/A_Walk_in_Elysian_Fields
House of Sticks - 11 - http://lanoire.wikia.com/wiki/House_of_Sticks
A Polite Invitation - 7 - http://lanoire.wikia.com/wiki/A_Polite_Invitation
A Different Kind of War - 7 -
http://lanoire.wikia.com/wiki/A_Different_Kind_of_WarUse the help to find all the clues of the game, when the music stop, you've got all the clues, if you hear the music, search always.To help you, go on the rockstar games social, and check the section
"case tracker"