You know everything Trophy in Subject 13

There are 27 testimonies in the game. Most of them you must obtain by finding yellow recording devices in each chapter, but some you will obtain during natural story progression. Whenever you pick one up and read it (you must choose to read it for it to register to your game), the border of the testimony text will tell you the percentage of testimonies found in the chapter (left side) and in the game total (right side).

You cannot revisit areas accessed in previous chapters. The game makes up for this by warning you that you're still missing testimonies if you try to finish the chapter, giving you an opportunity to back out and search for whatever you're missing.

Here is a breakdown of testimonies by chapter:

Chapter 1 – 2
Chapter 2 – 12
Chapter 3 - 8
Chapter 4 - 5

Following my walkthrough will get you all the testimonies: LINK