Damning Testimony has few investigators who want this because of the book requirement in Rogue. Without the Seeker 0-5 Rogue 0-2 Investigator, currently the only people who really want this are Trish, Finn and Alessandra, because they all have 4 book in Rogue, and also all benefit from enemies being alive already. Trish baseline gets an extra clue, Finn likes Evading, and Alessandra wants to Beguile enemies all over the board.
The closest comparison for this is actually Fingerprint Kit, because that is a high cost limited use item that gets you 2 clues in 1 action. The main value here, is that Damning Testimony gives 2 clues in 1 action in Rogue, which is kind of the best clue efficiency Rogue can ever get. Normally we look at Lockpicks or also Thieves Kit. Rogues' main value was getting additional actions to use, but Lockpicks was always once per round. Damning Testimony is also once per round. But the pros?
Pros:
- 2 clues on a success if there is an enemy at a location with a clue (it can be your location as well)
- You only spend evidence if you succeed (unlike Fingerprint kit, so you never lose out value on the autofail)
- Upgradable flexibility
- Illicit so you can dump this in your Underworld Market
- The important parts of Damning Testimony do not care about enemy Elite status.
Cons:
- Once per round
- 4 resource cost which is not nothing in Rogue
- Requires an enemy to be in play. This is important for some scenarios, and so this shouldn't be the only way to get clues.
- Limited uses (not as important when you consider you only spend if you succeed, so the uses always get you an extra clue
While there are 6 upgrades you can take, I personally only think 2 are of serious value, for 4 xp. Blackmail, to get a +2 to the test so you pass, and Fabricated Evidence, so you get 66% more value from your item. for 4 xp then, in the 4 investigators i mentioned, you're testing at 6 to shroud which is a great start to be in and 5 times you can get 2 clues over 5 rounds. This is really good considering its 1 handed, so you can still run something else in the other hand, be it a weapon, or a different item to help investigating such as a lockpicks or a thieves kit. or another Damning Testimony. Damning Testimony also goes up in value for quite a few scenarios if you know them, such as scenarios with patrolling enemies (Fortune and Folly), or chasing enemies (most of the Innsmouth campaign, that infamous train scenario)
Combined with Lockpicks to have something to do with your other 2 actions, I think this is incredible value for XP and Resources. The main problem to overcome is having enemies at the correct locations, which can be a problem to manipulate, but not insurmountable. Rogue now has 2 cards with Bonded enemies they can force into play (Crystalizer of Dreams, and Bianca die Katz). Trish can use Existential Riddle on Hunter enemies so they keep moving. Transmogrify can be used on 1 location to lock an enemy down. Alessandra has Beguile which lets her just move an enemy. Disguise Kit and multiple other effects can lock an enemy down for multiple rounds. But if you're looking to get some clue efficiency in Rogue, I think Damning Testimony is worth the run.