"Mm. This time ‘twas a mother                and ‘er daughter, in their own home.                Wee thing she was… it’s a shame.”

"Perhaps."

    [ Brona gave the stranger a friendly smile       and raised her glass in return, before bringing it to her lips. ]

"All I know is every time there’s a mysterious bloody murder, they think it’s ‘im come back. But I can tell ya, it ain’t. He only did whores."

"Ya think the Ripper’s really gone? Or jus’ changed his methods?"

Going along with the idea that 'Jack' was a resident of Whitechapel and a member of the lower working class, he'll be shown using colloquial speech, which will include 'street slang' as well as some incorrect or unappealing syntax. 

               A snicker passed the chief inspector’s lips, his eyes falling from the shadowy figure and focusing themselves on dirty concrete underneath his feet. Oh, if only solving this case would be that simple.

                 ❝No. Lipski’s methods were different       messier. And it’s                    obvious he hardly had any medical training beforehand.❞

           [ That wasn't precisely what Jack had been driving at, but he            grunted in acknowledgement. ] 

                          a ᴋɪʟʟᴇʀ

                                                   just for fun

               ❝ Honestly? It’s starting to make less sense with every victim.                 Yes, he does kill only unfortunate women, so far, but now I can’t                 seem to find the connection between the killing-spree that ended                 with Fair Emma’s death and the most recent one.❞

          [ Jack smiled. Settling his shoulder against the bricks of the wall           behind him  and  reaching  into his  pocket,  the man  withdrew a           bent cigarette,  shoved it between his lips,  and struck a match to           light it. ]

             ❝ Oh, I can hear his laugh in my                  own two ears. But how do I buckle him,                  hm? My hands are tied - Sir Warren                  won’t allow me to even question another                  surgeon or a simple doctor. And my boys,                  as you call them, are nothing good, truly.❞

          [ Jack was in a fit of enjoyment. Had he not been sure it would           end in  his arrest,  he would have ensured that  Abberline truly           did  hear  the  laugh of  the  Whitechapel  killer  in his  own two           ears. ]