"The legal system falls apart if jury members are honest. We approached twelve members of a jury, and paid them to bring down a guilty verdict. My competitor must have paid them more for innocent. Only because they took my money do I greenlight all of them. Take them out quick, or the authorities will catch on."
Madrazo paid a group of eight jurors to bring down a guilty verdict, but the group of jurors stole the money from Madrazo, not judging the verdict. The team now needs to take out four jurors around the city of Los Santos quickly, this means that all the players will have to separate themselves and make their own way to each juror. They are all in different places, all unarmed. After the team takes all the jurors out, Madrazo will send a message to each one of them that the cops are moving in to protect the four remaining jurors. Those four last jurors will be protected by the LSPD and the team will receive a three-stars wanted level by killing any one of them. After all the jurors are dead, only one player must lose his/her wanted level and go to Madrazo's mansion.
Take out the jurors.
Lose the Cops.
Go to Madrazo's house.
Arguably the fastest way to complete this mission is the following:
Get a full lobby of players. Anyone who owns a Buzzard should call it in. All players split up and kill the first group of jurors.
When the second group of jurors spawns, one player should lose their wanted level and work their way to Madrazo's mansion. This will save time since only one person has to lose their wanted level and get to Madrazo's to finish the mission.
As this player is moving towards Madrazo's everyone else again splits up and takes out the remaining jurors. When the last juror is killed, hopefully the player without a wanted level is already at Madrazo's, and the mission will immediately complete.
An alternative method for smaller teams is to have a player call for a Valkyrie Helicopter:
The pilot flies the attack chopper from target to target, the co-pilot assassinates the targets with the high explosive autocannon, and the door gunners deal with the Police Helicopters.
Once all targets are assassinated, have everyone equip rebreathers, parachute into the ocean, and dive deep underwater to quickly and easily lose your wanted level.
Call Merryweather for a quick ride back to the nearest shore, then find a car or call your Mechanic, and drive to Madrazos house. Only one person needs to drive Madrazo's house, so do not worry if there are not enough seats. Be mindful that if you attempt call your Mechanic a second time, there is a cooldown timer already in place which can make a quick delivery a tedious task.