U.S. Supreme court confirmations are a good time to reflect on some basic precepts of our "separation of powers" system of government. Like previous nominees, Sonia Sotomayor faced the Senate judiciary committee's firing squad, as partisan tensions played out over lifetime appointment to a court that has no retirement age. At 54 years of age, Sotomayor, whose nomination the full Senate votes on today, easily could serve for three decades.

More than any other single factor, this "until death do we part" constitutional requirement has been responsible for bruising and bitter confirmation battles. On the partisan chessboard, nailing down a lifetime supreme court spot is a major victory for your side.

Not coincidentally, justices are serving longer and longer terms. Between 1941 and 1970 the average justice's tenure was 12.2 years. Since then, the average term has been over 25 years. The average age of a justice leaving office has risen from 67.6 years to a very elderly 78.8 years. Currently two justices have been on the supreme court for more than 25 years.

Judicial term limits and mandatory retirement ages not only would make the confirmation process less partisan, it also would create a modest amount of turnover and ensure that one party or president does not stack the court. But more than the prospect of doddering, partisan judges is playing out in this crucial branch of government.

Supreme court justices are supposed to be "above the law", but as various decisions have shown, unfortunately that is not always the case. Too often the Nine Worthies reveal themselves to be just another partisan legislature - but an unelected one at that. In fact, in recent years following various decisions, many frustrated legal scholars have shaken their heads and muttered: "Five votes beats a reason any day."

The obvious partisanship of many decisions casts the supremes in a whole new light. If it's going to act like a legislature, then should its members remain unelected? Or if appointment remains the preferred selection process, should it be for a life term? And should the president remain the sole appointing authority, and the highly unrepresentative Senate the sole confirming authority?

Currently the president appoints and a majority of Senators confirms supreme court nominees. But multiple appointing authorities and higher confirmation thresholds would bring some balance to this "judicial legislature". Something like Germany's 60 % threshold for confirming justices would give the two major political parties a say over each other's appointments and help prevent a partisan takeover of the court.

Requiring 60 votes also would be an acknowledgement of how unrepresentative the Senate is. Of 100 senators, only 17 are women and five are racial minorities. A strong case can be made that a chamber as unrepresentative as the Senate should not be confirming lifetime appointments - especially not by simple majority vote. Doing so ensures that the unrepresentative features of the Senate spread to the high court.

Indeed, the subject of proportional representation on the supreme court - that is, the notion that the justices should, to some reasonable degree, reflect the ideological makeup of the country - is one that has not been considered enough. Of the current eight justices, it is likely that six are Republicans and two are Democrats, in a nation where partisan sympathies are fairly evenly divided and Democrats hold a decisive majority in the Congress. Six of the current justices were appointed by Republican presidents, only two by a Democratic president.

The term "liberal" always has been used rather loosely when it comes to the supreme court. In the narrow ideological spectrum applied to the court, justice John Paul Stevens, who was appointed by a Republican president and voted to reinstate capital punishment and to oppose affirmative action in the Bakke case, is a liberal. So is retiring justice David Souter, who voted to uphold a ban on gay Irish groups marching in the St Patrick's Day parade, and also voted that federal authorities may prosecute sick people who smoke marijuana on doctors' orders. A supreme court liberal is nothing like a Ted Kennedy or Jesse Jackson liberal.

Recognising the supreme court as an ideologically skewed judicial legislature helps us to understand how badly this crucial body needs to be updated for the 21st century. Judicial term limits, mandatory retirement ages, higher confirmation thresholds and multiple appointing authorities would ensure not only brilliant legal minds but also some balance of legal perspectives on the high court. And that would be good for America.