|Occupation||CEO of Hands of Asclepius|
|Japanese Name||Akihiro Nagasawa (長澤晃比呂)|
|Family||Tracy Mercer, Heather Ross|
- "Witness the power... of GUILT!"
Patrick Mercer is one of the main antagonists in Trauma Center: Under the Knife 2, alongside Reina Mayuzumi and Heinrich von Raitenau. He is the CEO of the HOA, or Hands of Asclepius, and claims to work towards changing the world of modern medicine. He is the stepfather of Heather Ross. Like Heinrich von Raitenau in X1, X2 and X3 and Reina Mayuzumi in X7, he is present to taunt the player during X4, X5 and X6.
Patrick Mercer is the head of the HOA, a group that creates doctors with an artificial healing touch to help combat against GUILT. While the HOA gets all the government and media attention, Patrick uses this to hide his true intentions to use Neo-GUILT to bring his wife Tracy Mercer, Heather's mother, back to consciousness after an accident left her in a coma several years ago. When his plans are exploited, Patrick activates Aletheia in Reina's body. However, Derek manages to defeat Aletheia. Soon after, Patrick attempts to escape, but is shot dead by the surrounding police.