Drink

[Barnaby]

Of course there's no evidence either way, but I suppose it comes down to if you think Jack was out late (increasing the probability that he was drinking) or up early on his way to work (decreasing it). If one accepts Jack as having disorganized attributes, these types are more likely to be under the influence. Also, alcoholism was rampant in the East End. I personally think it is more likely than not that Jack was drinking.

[Filby]

I agree with Lewis C and others. It is highly likely that JtR scouted out his victims in pubs when they had let their guard down from too much drink - that is unless you support the Astrikan man theory for the MJK murder. To win them over, especially with fear of JtR on the prowl, he would have to probably be a social drinker at least. He probably was also very good at identifying those that lost their financial support. Seems many of the victims had been recently estranged from their husbands or partners.

[I1ariusz]

Actually I'm not really guessing here myself but I will reference John Douglas profile of the Ripper: drinking lowers inhibitions. Also if Ripper was both hating and fearing women he would've find them more approachable after drink. And Like others said it's often the case that the killer is under some substance when he does what he does. 'In vino veritas' as the old Latin phrase says.