While knives are allowed and used in prison kitchens, they are not left loose for the prisoners to use as a weapon, as is done here. They are connected by a strong steel cable that barely allows the knife to go past the edge of the counter. Otherwise, one inmate can easily use the knife to wound or kill another inmate.
It is stated that Kipekemie Jara was convicted of criminally negligent homicide and sentenced to 20 years in prison with the possibility of parole after eight years, a way longer sentence than the law allows. Oz is set in Indiana, negligent homicide in Indiana is called reckless homicide, the maximum sentence allowed by law is only six years, the minimum is one year.
After Alvarez is locked into confinement, you can see his cell door move when he is pulling on it.
When Adebisi tells Wangler to slit the throats of the Sicilians in the cafeteria, a microphone pack is visible on his waist.