Board Thread:Theories/@comment-30785465-20170613200126/@comment-32443384-20180202025721

well humans were injected with the beast titan shifters fluid and were turned into somewhat abnormal titans. I would imagine that humans injected with the armored titans spinal fluid would not have the armor ability... but perhaps a human injected with the armored titans spinal fluid would become a normal or abnormal titan, and then injecting that titan again with the serum could grant it some hardening abilities despite it still being otherwise a normal or abnormal titan. That's not confirmed though, and it may be that only shifters can have other shifters abilities.

edit: I wrote this up, I think it covers pretty much everything.

Titan Injections: if one obtains the spinal fluid of a normal or abnormal titan and injects it into another human, that human automatically transforms into a titan. If one obtains the spinal fluid of a shifter of royal blood and injects it into a human they will not transform automatically, but only by the scream of the royal blooded person whose spinal fluid was used. Titans created by royal spinal fluid are bound to obey the commands of that royal blooded person, although control is not as complete as with the Founding Titans’ powers. If one consumes a titans’ spinal fluid rather than injecting it they become an abnormal, although abnormals can be made the normal way as well. If a shifter is injected with the spinal fluid of another shifter, they gain that shifters abilities; i.e. being injected with the Armored Titans spinal fluid grants another shifter the ability to harden their skin into a kind of armor.

It is not known what happens if one is injected with a non-royal blooded titan shifters spinal fluid, but likely results in normal or abnormal titans automatically, not needing their scream nor bound to their commands. It is not known what happens if one injects a normal or abnormal titan with the spinal fluid of a titan shifter, but likely either does nothing, or results in that titan gaining some form of that shifters abilities while maintaining relative mindlessness or abnormality. It is not known what happens if one is injected with the spinal fluid of a royal blood human or titan who is not a shifter, but royal human spinal fluid likely does nothing and royal pure titan spinal fluid likely results in normal or abnormal titans, not likely to be under the control of the normal or abnormal royal blooded titan who is itself likely mindless. It is not known what happens if a shifter is injected with the spinal fluid of a pure titan, likely nothing, nor what happens if a shifter is injected with the spinal fluid of a shifter of royal blood, perhaps they temporarily gain the abilities of royal blood shifters or perhaps nothing.