This paper distinguishes three ways in which speech is reported in the Greek of John's Gospel: directly (without the complementizer hoti), indirectly (with hoti and appropriate changes to first and second person references), and in 'hoti-direct' form (i.e., with hoti but without changes to first and second person references). The default way of reporting speech in Koine Greek is directly. Typically, when using direct speech, the reporter purports to reproduce the original speech verbatim. When in indirect form, the speech is not reported verbatim and/or is backgrounded with respect to what follows. The hoti-direct form is used to signal that the speech culminates some unit. When a reported speech is embedded in another reported speech, however, the use of hoti may be influenced also by the presence of hoti in the immediate context. When hoti follows the formula amen amen legô soi / humin 'truly truly I say to you' it signals that the assertion concerned makes explicit some previous point.
Levinsohn, Stephen H.
"Οτι recitativum in John’s gospel: A stylistic or a pragmatic device?,"
Work Papers of the Summer Institute of Linguistics, University of North Dakota Session: Vol. 43, Article 2.
Available at: https://commons.und.edu/sil-work-papers/vol43/iss1/2