A person that euthanizes research animals without authorization. This is often done on the grounds that it will end unnecessary suffering. In medical research a conflict of interest can arise, where the critical condition of an animal is deemed less revevant as squeezing as much datad as possible out of a model that was difficult to create*.
Blue juice commandos are rarely associated with animal rights activism or intentional sabotage or terrorism, as it's mostly carried out by people working within animal research facilities, with a vested interest in the work. These personnel must often deal with a conflict of interests, in that they are dedicated to the welfare of the animals but are party to the inherent suffering research causes other organisms for human embetterment.
Blue juice commandos are often highly competent in their injection technique, have an unrestricted or high level of access to controlled drugs - often due to the security clearance of their day jobs. They most often carry out these special ops during weekends or late at night to decrease the possiblity of detection.
Ironically the weekend is also when the most incompetent researchers in animal science carry out the most dubious procedures for the glory and the greater good of humanity.
"sorry sir, one of the rheumatoid arthritis research model was found dead in its cage this morning."
*The flaw in this situation is that data from an impaired animal is not accutate, it is for this reason that non-survival medical research is done on healthy animals rather than terminally ill vegan volunteers"
see blue juice and pentobarb 300 for more on this topic