Testimony in the trial of a 20-year-old accused of killing an Iowa City landlord in 2009 centered on a yellow legal pad Tuesday.

The piece of evidence, presented by the state, allegedly contains notes from Justin Marshall, who faces first-degree murder charges in connection with the slaying of John Versypt on Oct. 8, 2009.

Iowa City police Officer Michael Smithey, who worked on the case and who was assigned to interview Marshall, testified Tuesday.

Smithey mentioned the legal pad during a discussion about the importance of informants.

Smithey said he approached Antonio Martin — a man who came to know Marshall while serving a sentence for conspiracy to distribute crack cocaine — when he was sitting alone in the library at the Muscatine County Jail on Oct. 3, 2011.

Martin handed Smithey the yellow legal pad, which contained four pages of unexplained notes from Marshall, Smithey testified.

Smithey said he scanned the pages with a Wand Scanner pen and gave the notes back to Martin. He then asked the state for a warrant to search Marshall’s cell.

Three days later, Smithey said Marshall randomly called him and asked about the release of Charles Thompson, who was then incarcerated and charged with Versypt’s slaying.

After Thompson’s September 2011 first-degree murder trial ended in a mistrial, he pleaded guilty to accessory to a felony and signed documents stating he knew Marshall killed Versypt. The mistrial occurred after the prosecution played part of a videotaped interview with Thompson that officials agreed would not be shown to the jury.

Following the call, Smithey said he agreed to meet Marshall, but the conversation never occurred.

Thomas Gaul, one of Marshall’s defense attorneys, on Tuesday classified Martin, and all other informants, as “snitches” who should not be trusted.

Gaul asked Smithey if he believed being called a snitch is implying people lie. Smithey responded, “No,” but Gaul pressed the officer, questioning the credibility of using people in prison as sources.

“Everyone you talked to needed something,” Gaul said. “Everyone you talked to wanted something from the government.”

Smithey hesitated but agreed.

Additionally, Smithey spoke about his meeting with Carl Johnson, Jr., a prisoner and one of two other informants in the case. During the meeting, Smithey said he gave Johnson a list of suspects the state was investigating.

Gaul argued not only did the list allow Johnson to indict specific people, but he also could have circulated the names to other prisoners.

Beyond testimony about informants, the day’s witnesses also included Allison Murtha, a manager and forensic scientist at RJ Lee Group, based in Monroeville, Pa. Murtha testified further about a key issue in the trial: the presence of gunshot residue on Marshall’s clothes.

She explained the three types of residue and said one-component residue — the type found on the black and blue jacket Marshall wore the night of the slaying — can come from sources besides guns, like pyrotechnics. But the substance is rare, she said.

When the defense pressed Murtha on the possible source for the residue, she said the person in question could have discharged the firearm, been around the firearm when it discharged, or been in an environment or surface that came in contact with the residue.

Charles Brown, a resident of the apartment complex in which Marshall allegedly killed Versypt, started the morning by testifying about what he heard the day of the shooting.

Brown, who, Gaul charged, has changed his story throughout the investigation, stated he and his girlfriend had smoked marijuana earlier in the day and were watching TV when they heard a “popping sound.” Shortly after, Marshall was asking to enter their apartment, Brown testified.

Brown later said he had asked Thompson about the owner of the gun used to kill Versypt. Thompson said he bought the gun to “protect his family.”

The trial will resume today and is set to finish Friday morning. Marshall faces life in prison if he is found guilty.