Before reading this summary, please read the overview for context.
United States v. Allgire (2019)
Michael Allgire pleaded guilty to two drug offences (he was charged with at least ten) and was sentenced to 120 months and 233 concurrent months of imprisonment.  This sentence was reduced by 53 months for cooperating with the government.  After completing his sentence, Mr. Allgire violated the terms of his supervised release and was sentenced to six months in a halfway house. He left the halfway house after a single month.
Seven months later, Allgire was caught. The sentencing guidelines range for Alggire’s punishment was 5-11 months imprisonment; the government requested 9 months.  Judge Staci Yandl was less forgiving and inflicted two concurrent prison terms on Allgire of 17 and 24 months. [2-3] Allgire challenged this sentence, arguing that the total length was unreasonable and that the court should not have imposed the concurrent shorter sentence.
Judge Barrett cited U.S. v. Boultinghouse for the proposition that the court could only reverse the sentence if it was “plainly unreasonable.”  Barrett held that this was not the case, because the district court had clearly explained that its decision was based on several statutory factors: Allgire’s criminal history; his violation of supervised release; and the likelihood of recidivism. [3-4] Additionally, citing 18 U.S.C. § 3583, Barret explained that the maximum sentence available to the court was higher than 24 months. 
Allgire also argued that the court lacked the authority to impose two concurrent sentences. Because he had not argued this to the district court, Barrett reviewed it for plain error, which required Allgire to prove that the error “affected his substantial rights.”  The concurrent sentence would not increase the length of Allgire’s time in prison and the court rejected the argument that the stigma of a second counted as affecting his substantial rights. [5-6]
Therefore, Allgire will spend 24 months in prison.
United States v. Atwood (2019)
James Atwood pleaded guilty to three federal drug crimes. Judge Colin Bruce sentenced him to 210 months of imprisonment.
Like many judges, Judge Bruce was a former prosecutor, specifically an attorney in the U.S. Attorney’s Office in the Central District of Illinois [Bruce Report at 1] This was the same office that had prosecuted Mr. Atwood.  Unlike most of those judges, I hope, Bruce continued to exchange private messages with his former colleagues about their cases – including those over which he presided. [2-3] In total, Judge Bruce communicated with the prosecutor’s office ex parte at least 100 times, including such disturbing communications as: thanking prosecutors for persuading the court of appeal to affirm his decisions; reassuring and encouraging a prosecutor after a pre-trial conference; and lamenting that a prosecutor’s error had increased the likelihood that the defendant would be found not guilty. [2-3] Further examples can be found at pages 5-6 of the Bruce Report.
When all of this came out, Bruce was removed from all cases involving the U.S. Attorney’s office.  Two complaints were filed with the Judicial Council of the Seventh Circuit. A Special Committee was formed to investigate Bruce and Bruce was publicly reprimanded for violating the Code of Conduct for U.S. Judges [Bruce Order]. The Committee found no evidence that Bruce’s communications actually affected any of his decisions, however, and Bruce was returned to criminal cases in September of 2019. [3-4; Bruce Report at 6-8; Bruce Order]
There is no evidence that Judge Bruce ever discussed Atwood’s case with the U.S. Attorney’s Office.  On appeal, however, Atwood argued that Bruce should have recused himself. Although Atwood had not made the argument to Bruce himself, the court of appeals reviewed it de novo because Bruce’s improper communications had not been known at the time.  Judge Barrett concluded that, given the wide discretion enjoyed by district court judges, there was a substantial risk that Judge Bruce’s relationship with the prosecution had unfairly biased him against Atwood. [4-5] Re-sentencing Atwood, on the other hand, would impose only a fairly small administrative cost on the government.  Moreover, re-sentencing Atwood would encourage judges to communicate more judiciously in future, whereas letting the sentence stand would undermine confidence in the judiciary. [5-6]
Therefore, a different judge decided how long James Atwood will spend in prison.
United States v. Barnes (2018)
David Barnes was just fifteen years old when he was convicted of his first two felonies: robbery and aggravated discharge of a firearm. He was tried as an adult.  Over the ensuing years, Mr. Barnes would also be convicted three times for possessing marijuana and would smoke it in a public park at least once. 
Eventually, Barnes pleaded guilty to crimes relating to distributing crack cocaine. Based on his criminal history, which rendered him a career offender, he was sentenced to 269 months. [2 and note 1 on that page] At Barnes’ request, an Illinois court then converted his felony convictions at 15 to adjudications of delinquency. Barnes then asked the court to correct his sentence. Barnes no longer counted as a career offender but, at first, Judge Nancy Rosenstengel considered them as part of his criminal history. [2-3] After some back and forth, Barnes persuaded the prosecution to limit his criminal history to the four marijuana offences.  Barnes did not challenge the inclusion of smoking marijuana in a public park. On the contrary, he frequently listed it as one of the four minor crimes he had committed. [5-6]
Barnes’ reduced sentence was 189 months of imprisonment. He appealed, arguing that smoking marijuana in a public park did not count as an item of criminal history. He had violated a local ordinance but not (he contended) state law, so the violation should not have been used to enhance his sentence. Judge Barrett said that waiver principles should be interpreted in favour of the defendant but, even so, Barnes had (with good reason) based his strategy on his history of using marijuana. [4-6] He had expressly told the court to include the offence in his criminal history. Therefore, he had waived arguments against including it. [5-7]
Barnes will accordingly spend 189 months in prison.
United States v Briggs (2019)
Alandous Briggs was on parole when parole agents searched his home. They found marijuana, cocaine, a scale, and three loaded handguns. Mr. Briggs was willing to plead guilty to being a felon in possession of a handgun but not to admit that the guns were related to the drugs, which would lead to a longer sentence. Judge Tanya Walton Pratt accepted his guilty plea, held that the guns were related to felony drug possession, and sentenced Briggs to 84 months of imprisonment. [2-3]
The district court’s reasoning was not entirely clear. The court had mostly speculated that the guns were used in drug trafficking, therefore they must have been connected to the possession of cocaine. Judge Barrett held that this reasoning was not sufficient to connect the guns with possessing cocaine, emphasising that possessing guns and possessing drugs did not mean that the two were connected. [3-5]
Therefore, Briggs’ case was returned to the district court for re-sentencing.