Vandals left a pig's head at the former home of a Northern California use-of-force expert who testified for the defense in Derek Chauvin's murder trial at the weekend, NBC News reported on Monday, in a sign of the extreme tensions surrounding the case with the jury set to deliberate as early as Monday.

Forty-five-year old Chauvin, who is white, is charged with second and third-degree murder and second-degree manslaughter for the killing of George Floyd, 46, who is black on May 25 last year.

Authorities in Santa Rosa, California said the vandalism took place early Saturday morning at the one-time residence of Barry Brodd, a former Santa Rosa Police Department training officer, who moved out of the house many years ago.

"It appears the suspects in this vandalism were targeting Mr. Brodd for his testimony ... he hasn't lived at the residence for a number of years and is no longer a resident of California," the New York Post quoted the SRPD as saying.

Police said they received a call around 3 a.m. Saturday from the new homeowners who said they were awakened by a group of people all clad in black, who threw a severed pig's head on their front porch and drenched the front of the house with blood.

The same group of people are suspected to have doused a mall statue in animal blood around 45 minutes later and left a sign that read, "Oink Oink," authorities said. They have not been identified and are accused of felony vandalism.

During his testimony, Brodd said he believes former Minneapolis officer Chauvin's restraint of Floyd was in accordance with standard police practice and training.

"That isn't an incident of deadly force," Brodd said, according to AP. "That's an incident of an accidental death."

Brodd's testimony countered a string of several Minneapolis Police Department use-of-force experts and top officials who said the amount of force Chauvin applied on Floyd was "excessive and unnecessary."

"His comments do not reflect the values and beliefs of the Santa Rosa Police Department," Santa Rosa Police Chief Rainer Navarro said.

Meanwhile, the prosecution and defense have each rested their cases and both sides are set to deliver their closing arguments Monday.