The appointment of judges is an important issue for any designers of a constitution. Perhaps it is the most difficult aspect of constitutional design. The principal aim of the judiciary is to provide a check on the other branches of government, which is necessary as – according to classical republicanism – power corrupts. A system of checks and balances is an essential feature of a republican constitution.
However, in practice it seems difficult to ensure full independence of the judicial branch. In my opinion the main issue is in the selection of judges, in particular the selection of judges of supreme courts. In most countries judges are appointed by the executive with or without approval by the legislature. The backside of this process is that pro-government judges are more likely to be appointed and hence weakening the separation of powers.
Also, probably a greater issue, is that the appointment of judges becomes politicized, as is clearly demonstrated by the recent appointment of Gorusch to the US Supreme Court. This politicization of the judiciary even further undermines the independence of the courts and henceforth the system of checks and balances.
Ideally, elected politicians would not to be involved in selected judges at all. So what alternative options to we have for selecting judges?
One option, hereditary succession, is problematic for two reasons. First of all, it creates a privileged class of citizens, which is at odds of the very principles of liberalism and republicanism. Also hereditary succession no guarantee that competent judges will be selected.
Another option, election of judges by popular vote is also problematic. If judges are subject to public opinion, i.e. in order to be reelected, their verdicts might be determined on what is popular as opposed to fairness. For example, a judge might be tempted to convict a suspect not on the evidence presented, but on the public perception of guilt. The consequence of this is an increased risk of miscarriages of justice.
co-option is the method where judges will appoint other judges. At first this seems to be a good option. However, the risk with this method is that judges will select colleagues who share their own views and this might result in a conservative judiciary, whose view might grow over time at odds with the rest of society.
(Some might say I used two contradictory arguments in the previous paragraphs. However, this is only superficial. Courts should keep a certain distance from public opinion, but should not simultaneously ignore it completely.)
An interesting option would be democratic appointment. This method works as follows. A jury of randomly selected citizens will appoint or nominate a judge whenever there will be a vacancy. Because the (elected) politicians are no longer involved in the appointment process, the independence of the judiciary is strengthened. Meanwhile the perils of direct election or co-option are also avoided.
This appointment jury will interview prospective candidates in order to establish they are suited to serve as a judge. Subsequently the members of the jury will deliberate who they will appoint or nominate to fill a vacancy.
Besides judicial appointments, this method could be used to select other important officers, e.g. the members of the board of the national monetary authority.