All eyes will be on the Supreme Court this week, as it closes its term by handing down some of the most anticipated decisions of the year.

Because the court tends to release the "blockbuster" decisions during the last few weeks of June, the end of term offers a vivid reminder of how closely divided it is on the most important issues. This reminder should be all-the more stark this year, given the aging court membership and the distinct possibility of multiple retirements during the next presidential term.

Chief Justice Roberts deserves tremendous credit for cobbling together majorities this term that cross traditional ideological lines. To date, only about 15 percent of the cases decided this term have been by a 5-4 vote. But the summer of love had to end sometime, and Boumedienne, which granted detainees in Guantanamo the right to petition for relief in any federal district court they choose, revealed the deep fault lines in the court.

Other contentious cases wait on the horizon, including Kennedy, which asks whether a state may impose the death penalty for the rape of a child, and Heller, a challenge to the District of columbia's handgun ban. Given the divisions on the court, it's likely that at least one of these cases will be decided 5-4.

If the tea-leaf readers are correct, the Supreme Court will recognize a limited individual right to gun ownership. This will mean more litigation, as challenges are mounted to the varying regulations in localities throughout the country. In the coming years, the court will likely have to readdress this question, during which it may enlarge or constrict the right.

Similarly, the Guantanamo case - a striking case of judicial overreaching which provided no guidance to lower courts as to how to review the detainees' claims - promises to spawn numerous cases destined for the Supreme Court. Add to this the increasing litigation over the question of the right to same-sex marriage, and the Supreme Court is likely to have a healthy diet of detainee, gun and marriage cases seeking its attention in the coming years.

The question, then, is what the court will look like. There is much discussion about the possible retirement of Justices John Paul Stevens (88 years old) and Ruth Bader Ginsburg (75) in the next administration. However, when the next president is inaugurated, six members of the Supreme Court will be age 69 or older, and by Election Day 2012, those six justices will range in age from 74 to 92.

Included in that list are conser-vative-leaning Justice Antonin Scalia, who will be 76 by the end of the next presidential term, liberal-leaning Justices David Souter (by then 73) and Stephen Breyer (then 74), and the frequent .fth vote in 5-4 opinions, Justice Anthony Kennedy will be 76. Based upon the aging membership of the court, the common refrain of two retirements in the next administration may in fact be too low.

The retirement of Stevens or Ginsburg and their replacement by a liberal president and Congress would cement the current divisions on the Court for years to come. But there is a far worse possibility for conservatives: If Scalia or Kennedy retires and is replaced by a consistently liberal vote, then the balance of the court shifts. Currently, the 5-4 votes are neither consistently liberal nor conservative. Another liberal vote on the court, though, would change that.

Of course, the Supreme Court is just the tip of the judicial iceberg. While the Supreme Court's decisions undeniably have tremendous impact, the court chooses to hear only about 70 cases per year out of roughly 10,000 requests for review. Given this (appropriately) small docket, the Courts of Appeals are ordinarily the courts of last resort for litigants, and thereby establish much of the case law that governs Americans on a day-to-day basis.

It is therefore telling that the 4th, 5th and 6th Circuit Court of Appeals, which cumulatively cover 11 states, are almost evenly divided. You can call them 5-4 circuits. The next president will be able to shape the direction of these courts for years to come.

The Guantanamo case left conservatives nervous about the razor-thin balance of the Supreme Court, and its increasing willingness to insert itself into national security questions properly reserved to the other branches. This nervousness is warranted. But given the aging membership of the Court, even greater uncertainty lies ahead.

Robert Alt is a senior legal fellow and deputy director of the Center for Legal and Judicial Studies at The Heritage Foundation (heritage.org).