Aaron Hernandez Trial: Prosecutors Continue to Detail Police Evidence Tying Him to Murder

— -- A Massachusetts police sergeant testified today that he recovered a piece of chewed gum and bullet shell casing from a garbage dumpster -- evidence prosecutors have insisted tie former NFL star Aaron Hernandez to the murder of Odin Lloyd.

But the defense hammered away at the point that police mishandled evidence in the case -- causing DNA contamination on some items such as the gum that allegedly belonged to Hernandez.

Sgt. Paul Baker, who works for the Massachusetts State Police, said the items he recovered were removed and photographed as evidence.

The gum and shell casing had originally been thrown out by a National Rent-a-Car employee in North Attleboro who had cleaned up a vehicle Hernandez had rented around the time of Lloyd's murder.

At one point, Hernandez, 25, could be seen staring at a TV monitor displaying the items police had collected while Baker testified.

Hernandez's lawyer James Sultan grilled Baker on cross examination about his methods, asking him why the items collected from the trash had not immediately been placed in an evidence bag.

"You're not part of crime scene services, correct?" Sultan asked.

"Yes," Baker replied, adding that the items had been placed in the back of a truck before they were bagged.

In his testimony, Baker also said because of the "media frenzy," investigators went unnoticed at the car rental office since they did not wear their "State Police" jackets.

Hernandez is charged in Lloyd's death in June 2013. Lloyd, 27, was dating the sister of Hernandez's fiancee at the time.

Lloyd was shot with a .45-caliber gun. No weapon has ever been recovered.

Also today, prosecutors showed blurry video surveillance of what they said was Hernandez in a car picking up Lloyd a day before his body was found.

The testimony came a day after three state troopers told the jury about the evidence they collected.

State Trooper Zachary Johnson testified about going to Lloyd's home the evening his body was found and telling his family that he was dead. He also spoke about a safe police found in the closet of Hernandez's master bedroom. Once inside, Johnson recalled, he came upon the digital scale and dish.

Johnson said investigators also recovered four pairs of white Nike Air Jordan sneakers. Prosecutors have said a footprint by an Air Jordan sneaker was found at the crime scene.

Trooper Joseph Collins testified about picking up Hernandez's BlackBerry phone from Hernandez's lawyer on June 18, 2013, the day after the murder, while Trooper John Conron detailed how he recovered a digital recorder that held video surveillance from the former New England Patriots' player home.

The Associated Press contributed to this report.

Get real-time updates as this story unfolds. To start, just "star" this story in ABC News' phone app. Download ABC News for iPhone here or ABC News for Android here.