Board Thread:Naruto Discussions/@comment-26403664-20160228225013/@comment-681696-20160315115733

My point was that an absence of evidence is not evidence of absence.

We are never told in canon what is require to use PS so you can't say for a fact that Itachi is incapable of using just like I can't say for a fact that Itachi could use PS you are making a assumption that EMS or Six Paths chakra is required.

Personally I feel that if MS isn't all that is required to use PS that Indra's chakra is probably the reason they could use it with Obito getting some of Indra's chakra from using Madara's eye as opposed to two diffrent reasons people were able use PS.