If D1 can't sue D2, then wouldn't D1 and D2 argue identically that D3 broke the chain of causation?

Question

I deliberately hedged each defendant's possible negligence.

D₁ (Defendant 1) might've negligently injured P. P falls to the pavement, and bleeds. D₁ panics, and runs away. D₁ is a billionaire.

Next, D₂ might've negligently injured P too. After perhaps negligently injuring P, D₂ drives P to a hospital’s emergency department ("ED"). D2 is bankrupt. D2's net worth is merely $900.

The ED's lone overworked doctor, D₃, might've negligently injured P too. 9 hours after being admitted to the ED, P dies.

Discuss merely all parties’ tortious liability. Ignore — do NOT discuss — damages. Assume that D1 shall NOT sue D2, because D2 is bankrupt and beggared. But D2 can still sue D3.

D1 and D2 shall try to argue that D3 broke the chain of causation.

1. But wouldn't D1's and D2's argument that D3 broke the chain of causation, be the exact same? If not, why not?

2. In other words, imagine that D1 wrote a Statement of Defence before D2. After changing D1 to D2, can't D2 just copy and paste D1's Statement of Defence?

Answer 1

Yes. D3's actions potentially break the chain of causation with respect to both D1's liability and D2's liability. The same reasoning could be used by both of them.

None of that depends on whether any of the defendants sue each other, though. If someone sues D1 or D2 on P's behalf, they each could argue D3 as a break in the causation. D3 does not need to be a defendant nor a included as a third party in order for D1 or D2 to rely on D3's acts in their defence.

D2's statement of defence would likely not be a straight copy of D1's, since D1 will likely have also have argued that D2's actions broke the chain of causation. But with respect to the effect of D3's actions, D1 and D2 could make the same argument.

None of the above assumes anything about the likelihood of success for D1 and D2. It only says that they'd have the same argument available with respect to D3.