In the upcoming death-penalty trial of Gary Lee Sampson, jurors will hear that he carjacked two people in Massachusetts more than a decade ago, that he tied them up, and that he brutally stabbed them to death. They will hear that he strangled a third man in New Hampshire before pulling a knife on another in Vermont.

But the jury will also hear about Sampson’s troubled life — that he suffers from mental illness, that he was diagnosed at age 7 with dyslexia, that his parents grew up poor, and that his father frequently disapproved of him.

Such bits of information are known as mitigating factors, and Sampson’s defense team hopes to present an unprecedented 238 such points to the jury charged with deciding whether Sampson will be sentenced to life in prison, or death. Mitigating factors are meant to explain a defendant’s actions and guide a jury away from a death sentence.

Jury selection continues this week.

As US District Judge Leo T. Sorokin explained to potential jurors earlier this month, a mitigating factor can be “anything that suggests that life imprisonment without the possibility of release is more of an appropriate sentence than death.’’

Sorokin will ultimately decide how many mitigating factors can be presented to the jury on the verdict slip. But in the meantime, the number of factors being proposed by Sampson’s defense is leading to questions in the case about what exactly constitutes a mitigating factor, and whether jurors should be asked to consider so many of them.

“It’s an everything but the kitchen sink strategy, hoping one juror will seize on one factor and find it to be mitigating,’’ said George Vien, a lawyer who prosecuted Sampson in his first death-penalty trial 13 years ago.

Prosecutors argued that some of the factors “have nothing to do with Gary Lee Sampson’s background, record, character, or the circumstances of Sampson’s offenses, and thus are not relevant to the individualized sentencing decision the jury must make regarding Sampson,’’ according to previously sealed court records.

Sampson was sentenced to death in 2004, but a judge later threw out the sentence after finding that one of the jurors lied during jury selection. Prosecutors are again seeking the death penalty in the new trial about to get underway. The trial could last 10 weeks, and jurors will hear not only testimony about Sampson’s crimes, but also from the families of his victims, and about violent incidents he’s been involved in while in prison.

The defense is expected to argue that Sampson suffers from mental illness, and that his condition was exacerbated by drug and alcohol abuse and years spent in solitary confinement in prison.

Among the mitigating factors the defense hopes to present: That Sampson suffered head injuries as a child that contributed to brain damage; that he did not know the alphabet by age 7; that his father, a war veteran and an alcoholic, was frequently ashamed of Sampson and physically disciplined him; that he was beaten up by peers but did not fight back; that his mother married at age 18 and was subservient to his father; that he suffered anxiety and abused drugs as a teenager; that his time spent in isolation in prison before the killings worsened his mental health; that he is divorced and never had a relationship with his children; that he wants love and wanted to be loved; that in the days before the carjackings, he was abusing alcohol and crack cocaine; that he suffers from illnesses including cirrhosis of the liver; that making art helps him cope with prison life.

George Kendall, a New York-based lawyer who has worked on hundreds of death penalty cases, including for the American Civil Liberties Union, said the lengthy list of factors appears to be “communications strategy,’’ a way for the defense to connect with the jury and respond to the list of reasons prosecutors cite in requesting the death penalty.

“What you hope to do is package the case in a way that the jury accepts it,’’ he said, adding that the defense team likely determined that the longer the list, the better the package.

Vien, the former prosecutor, cautioned against listing common life occurrences that jurors would not consider to be serious mitigating factors.

“The problem is some of these factors are arguments that aren’t going to have much substance to them, and the lawyers who put those arguments forward risk losing credibility among those jurors,’’ he said. “I feel it’s always better to go with fewer, more solid arguments than several arguments which won’t have much merit.’’

The proposed 238 mitigating factors would be the most ever presented to a jury, according to data compiled by the Federal Death Penalty Resource Counsel, which tracks federal capital punishment cases. The majority of cases list anywhere from 20 to 40 factors. In Sampson’s original trial in 2003, jurors reviewed 17 factors. Jurors who sentenced Boston Marathon bomber Dzhokhar Tsarnaev to death last year considered 21.

The federal case with the most mitigating factors presented to a jury, 160, was that of John McCluskey, who was convicted in 2013 in New Mexico of the carjacking and murder of an Oklahoma couple.

He was sentenced to life in prison after the jury failed to reach a unanimous decision on a sentence.

One of McCluskey’s lead lawyers, Michael Burt, also represents Sampson in his new sentencing trial.

Last year, federal prosecutors asked Sorokin to force the defense team to reduce the number of proposed mitigating factors, and called the lengthy list a “strategic attempt to confuse the jury by impermissibly skewing the weighing process in Sampson’s favor.’’

Sampson’s lawyers lashed out, saying the Supreme Court has referred to mitigation as “potentially infinite’’ and as having “virtually no limits.’’

While rejecting some of the government’s claims, Sorokin asked the defense to trim the list — the number was reduced earlier this month to 238, from 308 — and the judge suggested that the definition of mitigation will be reexamined as the trial progresses, and before a final verdict slip is presented to jurors.

“The court does not consider this definition to be boundless as Sampson urges,’’ the judge said. “Rather, the information presented to the jury may be properly and constitutionally limited by notions of relevance in the context of this case.’’

Milton J. Valencia can be reached at milton.valencia@globe.com. Follow him on Twitter @miltonvalencia.