WASHINGTON, Oct 7 (Reuters) - The U.S. Supreme Court kicked off its new nine-month term with a flurry of activity on Monday, hearing arguments in three cases and rejecting numerous appeals that piled up over the summer.
With conservative Justice Clarence Thomas absent due to an unspecified illness, the court began hearing its first argument in a case focusing on whether states can discard the so-called insanity defense in criminal prosecutions. The case involved a man sentenced to death in Kansas for fatally shooting four family members while suffering from severe depression.
In remarks from the bench before the first argument, Chief Justice John Roberts said Thomas, the court's longest-serving justice, was "indisposed" due to illness but would still participate in deciding the three cases.
Details of Thomas' illness were not immediately disclosed. Thomas, one of the nine-justice court's most conservative members, is 71 and has served on the court since 1991.
In another action of note, the court said it would go ahead and hear a challenge to New York City restrictions on handgun owners transporting their firearms outside the home.
The city had argued over the summer that because the measure - challenged by gun owners and the state's National Rifle Association affiliate - was recently amended, the case before the justices was moot and there was no reason for the Supreme Court to hear the matter.
The justices in a brief order said they would consider that argument when they hear the case on Dec. 2, leaving open the possibility they will toss the case later.
The court hears its first major case of the term on Tuesday on whether a landmark decades-old federal anti-discrimination law that bars sex discrimination in the workplace protects gay and transgender employees.
Abortion rights also will figure prominently for the justices in the coming months. The court on Friday agreed to take up a major case that could lead to new curbs on access to abortion as it considers the legality of a Republican-backed Louisiana law that imposes restrictions on abortion doctors.
Another major case to be heard on Nov. 12 is over Trump's move to end a program created by his Democratic predecessor Barack Obama that protects from deportation hundreds of thousands of immigrants - mostly Hispanic young adults - who were brought into the United States illegally as children.
The other two oral arguments scheduled on Monday are on whether the U.S. Constitution requires unanimous jury verdicts and on fees in patent litigation.
The court will issue rulings in all its cases by the end of June.
The court declined to hear several appeals. One involved Amazon.com's bid to avoid a lawsuit seeking to ensure that warehouse workers for the e-commerce giant get paid for the time it takes them to go through extensive post-shift security screenings.
It also refused to hear Las Vegas sports gambler William "Billy" Walters' appeal of his 2017 insider trading conviction that landed him a five-year prison sentence in a case that also drew attention because of his ties to billionaire investor Carl Icahn and golfer Phil Mickelson.
The court declined to hear a bid by Sempra Energy's San Diego Gas & Electric Co to recover $379 million from customers related to damages it was forced to pay out in litigation after the deadly 2007 California wildfires that burned hundreds of homes.
It opted not to hear Acorda Therapeutics Inc's appeal of a lower court ruling that allowed generic versions of its multiple sclerosis treatment Ampyra and caused the drug's sales to plummet.
The justices refused to hear a bid by the University of Wisconsin's patent licensing arm to reinstate its legal victory against Apple Inc in a fight over computer processor technology that the school claimed the company used without permission in certain iPhones and iPads.
They also declined to take up a dispute over the assets of Puerto Rico's largest public sector pension fund.
Reporting by Larence Hurley and Andrew Chung; Editing by Will Dunham