Based on the provided legal document, the key points are as follows:

1. A Third Party Notice can be issued without prior court leave against a party already involved in a suit under O 16 r 8 of the Rules of Court 2012, specifically when claiming indemnification or contribution (!) (!) .

2. The issuance of a Third Party Notice against a party who is already a defendant in the same suit does not require court approval if the claim is for contribution or indemnity, and such notices can be served against co-defendants without seeking leave (!) (!) .

3. The procedural distinction between issuing a Third Party Notice under O 16 r 8 and other provisions (such as O 16 rr 1 and 2) is significant. Notices under O 16 r 8 are aimed at parties already involved in the action and do not require leave, whereas notices under other rules may require court approval depending on the circumstances (!) (!) .

4. The court emphasized that a Third Party Notice can only be issued against a person who is not already a party to the action. Once a party has been added to the suit, they cannot be served with a Third Party Notice under the same procedural rule (!) (!) .

5. The doctrine of res judicata and estoppel may prevent a party from raising the same issues in subsequent proceedings if those issues have already been decided in earlier cases. However, in this context, the court clarified that procedural missteps (such as filing under the wrong rule) do not necessarily bind the party if the underlying right to issue the notice remains valid (!) (!) (!) .

6. The court distinguished between claims for contribution or indemnity that are part of the main counterclaim and separate claims that are independent. Claims for contribution or indemnity are generally connected to the main action and cannot be brought as separate actions if the main claim is unresolved (!) (!) (!) .

7. The issuance of a Third Party Notice under O 16 r 8 does not require leave if the claim fits within the scope of contribution or indemnity against a party already involved in the suit. Nonetheless, procedural errors or misapplications of the rules can lead to dismissals, but these do not necessarily negate the underlying right to issue such notices (!) (!) .

8. The court reaffirmed that the purpose of Third Party Notices is to resolve all related issues in one proceeding and prevent multiplicity of actions, but procedural compliance is critical to their validity (!) (!) .

In summary, the document underscores that a Third Party Notice can be issued without court leave against parties already involved in the same suit when claiming contribution or indemnity, provided procedural rules are correctly followed. Filing under the wrong procedural rule may lead to dismissals, but does not inherently bar the underlying right to serve such notices if the procedural requirements are ultimately met.