London, England (CNN) -- Lockerbie bomber Abdelbeset al-Megrahi is "a very sick man," but there is no way to tell how long he will live, according to the father of one of the people who died in the 1988 bombing of Pan Am Flight 103.
Jim Swire, whose daughter Flora died in the terror attack, saw al-Megrahi a week ago in Libya, he said Tuesday.
He also criticized U.S. senators who tried to hold hearings this summer into questions surrounding the release of al-Megrahi.
He said he had written to them to say it was more important to let Scottish legal proceedings run their course, since a review commission had found possible miscarriages of justice in the case.
"They didn't want to know about that," he said of the senators, saying they had not replied to his letter.
The Scottish government released al-Megrahi from prison just over a year ago on the grounds that he had cancer and was not likely to live more than three more months.
Swire, who does not believe that al-Megrahi is guilty, defended the decision.
"At three months, just over half [of people with his cancer] would be dead," Swire said.
But after three months, mortality rates level off, and there is no way to predict how long cancer sufferers will live, said Swire, a retired general practicioner.
"He can walk a few steps," Swire said of al-Megrahi.
He did not ask al-Megrahi or his doctors about the Libyan's medical condition out of respect for his privacy, he said.
But he said the fullness of his face suggested that he was on steroids to slow the cancer.
Al-Megrahi was appealing his conviction when he was freed on compassionate grounds in August 2009 and then dropped the appeal.
Swire thinks al-Megrahi feels guilty about having withdrawn his appeal, since it leaves him with no way to clear his name or for those -- like Swire -- who think he is innocent to have the case reviewed.
But al-Megrahi's death could change the legal playing field, Swire speculated.
"If he were to die, the the situation would change," and Swire might be able to get the case reopened, he said.
He believes that al-Megrahi "would see to it that we would be provided with all the information his defense team has assembled," he said, adding that the Libyan had not explicitly told him that.
Swire is in the minority among victims' families in thinking al-Megrahi is innocent.
American officials blasted al-Megrahi's release at the time and on the first anniversary.
"As we have expressed repeatedly to Scottish authorities, we maintain that al-Megrahi should serve out the entirety of his sentence in prison in Scotland," Secretary of State Hillary Clinton said in a written statement.
President Barack Obama's assistant on homeland security and counterterrorism, John Brennan, called the release "unfortunate and inappropriate."
Democratic Sens. Robert Menendez and Frank Lautenberg noted that al-Megrahi was only given three months to live when he was released but is still alive.
Menendez noted that on August 20, 2009, al-Megrahi stepped off a plane into the arms of a cheering throng in Libya.
"A mass murderer tasted freedom, experiencing joy," Menendez said. "It was a scene that made the stomach turn ... that made old wounds fresh again in the hearts of those whose family members died at the hands of that man."
Lautenberg said, "It is the families of those victims who deserve compassion, not this terrorist."
"Al-Megrahi ... is very much free, living in the lap of luxury by all accounts," Menendez said.
The case has outraged many on both sides of the Atlantic and led U.S. senators to demand answers from Scotland about the details of his release.
Al-Megrahi is the only person convicted in the bombing of Pan Am Flight 103, which exploded over Lockerbie in December 1988, killing 259 people on the plane and 11 on the ground.
Most of the dead were Americans. The flight had been heading to New York from Frankfurt, Germany, via London, England, when it blew up.
A special Scottish court in the Netherlands convicted al-Megrahi in 2001.
CNN's Melissa Gray contributed to this report.