The family of Kaylee Goncalves is pissed over the plea deal offered to accused murderer Bryan Kohberger … and they are taking shots at prosecutors.

The Goncalves family tells TMZ … “The death penalty is merely an illusion in the criminal justice system. When available, it serves as a bargaining tool for the State, and when rarely applied, it’s never enforced due to a highly inefficient appellate process.”

As we reported … Kohberger will plead guilty to four counts of first-degree murder, but prosecutors will take the death penalty off the table and recommend life without the possibility of parole.

The Goncalves family tells us … “We questioned decisions early in the investigation: why was the mayor commenting on the case? Why was the coroner speaking to families? Why was an officer with less than two years’ experience leading the investigation? Why was the University of Idaho involved when they declared it an isolated off-campus incident? Why was the University permitted to write a book about the incident while others were silenced under an overly broad order?”

Kaylee’s fam continues … “As a result, we were branded adversaries. So, it was no shock how the Latah County Prosecutor’s Office mishandled the plea deal. They vaguely mentioned a possible plea on Friday, without seeking our input, and presented the plea on Sunday.”

They add … “Latah County should be ashamed of its Prosecutor’s Office. Four wonderful young people lost their lives, yet the victims’ families were treated as opponents from the outset. We weren’t even called about the plea; we received an email with a letter attached. That’s how Latah County’s Prosecutor’s Office treats murder victims’ families.”

The family says prosecutors are “adding insult to injury” by “rushing the plea, giving families just one day to coordinate and appear at the courthouse for a plea on July 2. Who do they think they are?”

Kaylee’s family says they are frustrated because “after more than two years, this is how it concludes with a secretive deal and a hurried effort to close the case without any input from the victims’ families on the plea’s details.”