Judicial independence is ensured in the Constitution of the United States of America in the following ways :
The federal judges may be removed only by impeachment and conviction of treason, bribery, or other high crimes Judicial impeachments are conducted by the House of Representatives and require conviction by the Senate. They are very rare. The process is deliberately difficult, to guard against judges being impeached for political reasons.
Article III of the Constitution further ensures that compensation for federal judges “shall not be diminished during their continuance in office.” Neither Congress nor public opinion can “punish” a judge for an unpopular decision by threatening his paycheck. With an assured salary and permanent tenure in a respected office, judges have no real incentive to abuse authority so they are much more likely to discharge their duties faithfully.
Judicial independence is also enhanced by the selection process for federal judges. Federal judges are appointed by the president when vacancies occur. They must be confirmed by a majority vote in the Senate before taking office. Presidential appointments of judges leave a visible and important legacy, so presidents carefully consider those whom they select based on certain criteria presidents' reputation, judicial record, experience, ideology, loyalty, etc.