Judgment Effect
Merger in Judgment
A related principle to res judicata prevents the claimant obtaining a  second judgement on the same matter. This is not based on estoppel, but on the principle that his claim has merged in the judgement.
Similarly, where the plaintiff’s claim, if adjudicated later might have been more extensive and awarded greater damages (e.g personal injuries have taken and unforeseen turn for the worst) , the matter may not be reopened, as the order has concluded it.
Where persons are jointly liable without also being severally liable recovery against one will preclude the plaintiff from proceeding against the other persons who are also jointly liable. This is because  the single cause of action has merged in the judgement.
Requirements for Merger
Merger will not take place unless the same claim or cause of action arises in both cases. The claimant must have had the opportunity of recovering in the first matter what he seeks to recover in the second.
Where the  claim relates to different circumstances or where for whatever reason it was not possible to have sought the orders in the first proceedings, the principle does  not apply. In the case of judgement in rem by a competent court, which is final, the matter is conclusive in respect of the subject matter concerned.
Third parties are bound by the result notwithstanding that they are not the party to the proceeding. The judgement must be limited and in accordance to the jurisdiction of the court and the State within which it is situate.
Who Bound
A judgment in personam is a judgment between the parties to litigation which determines the rights in respect of a matter in dispute. Judgements in personam bind the parties to the litigation only.
It does not declare status or interests except as between the parties. Judgements in personam include all judgements which are not in rem. They do not affect the rights of a third party.
A judgement between parties in personam raises an estoppel between the parties and their successors privies who derive title from them, only. In this context privies are ancestors and descendants (privies in blood), privies in law (including persons and their legal representatives such as bankrupt and trustee in bankruptcy and privies in estate (being successive property owners, assignor and assignees).
Privies
It is not enough that the parties have similar interests. One must  derive title from the other.The succession in title of privies must arise after proceedings.
Judgements are binding on privies in the same capacity as their predecessor. Where they sue in a different capacity the principle does not apply. Trustees and their beneficiaries are privies.
Although not strictly privies, some parties’ interests are shown derivative from those of another that they are bound as quasi privies. An indemnifier and indemnified person are privies as regards a third party actions against the party indemnified.
Estoppel must be mutual. Each party to the second proceedings must have been party or privy to the earlier proceedings.
In Rem
Judgements may be divided into two classes. Judgements in rem bind all persons.
Judgements in rem exist only in a narrow number of categories relating to property, admiralty and the status of persons and things. A judgement in rem determines the status of a person or thing or the disposition of a thing, as opposed to the relative interests or rights of the parties to the litigation.
A judgment in rem may declare status or title, forfeiture, condemnation or sale. They are a particular feature in admiralty matters, which might, for example, involve the establishment of a lien or the condemnation of a vessel as prize. It may declare the status of a person, such as probate, divorce or nullity. Further examples include adjudication of bankruptcy and similar declarations of status.
Some types of orders are not judgements in rem, although they may appear to have some of the requisite characteristics. These include an order to wind up a company, a coroner’s inquisition and a decree of legitimacy.
In Rem and Privies
A case in rem is conclusive in relation to the matters decided. It does not extend to incidental or implied matters. An example of an order in rem is the grant of probate proving a will in solemn form (i.e., by court order). The essential parts of the judgement are only binding on third parties.
A judgement in rem given by consent is unlikely to  bind third parties. An act or agreement between third parties does not usually  not bind others.