Dattatreya, among others, is an ideal example of a Jivanmukta. He was always associated with wine etc and a filthy lifestyle.
Why is that?
Because Jivanmuktas don't want the masses to come to them. As simple as that. Because their touch is enough to liberate others, but not everyone is ready for liberation yet.
Symptoms from Upanishads:
Like Svetaketu, Rbhu, Nidagha, Vrsabha, Durvasas, Samvartaka,
Dattatreya, and Raivataka, he has no visible emblem; he keeps his
conduct concealed; he acts as if he were a fool, a lunatic, or a
goblin; and, although he is sane, he behaves like a madman.
Narada Parivrajaka Upanishad, Chapter3
In these Upanishads, they are known as Paramhamsas. They always will hide their true identities. And, they will do everything so that people feel disgusted towards them.
His emblem and aim concealed, he should present himself to the people
as a madman or a simpleton even though he is a sage, and as a fool
even though he is wise. "Let him not do anything, say anything, or
think of anything whether it is good or bad. In this manner a sage
shall roam like a fool, finding his delight in himself.
Although he is sane, he behaves like a madman. He has no visible
emblem. He keeps his conduct concealed.
Paramhamsa Parivrajaka Upanishad, Chapter 5
So, we can not recognize such a person neither from his conduct, nor from what he is wearing.
Symptoms from VedAntic texts:
I'm using YogaVAshita here.
Dure munchati vandhumandhamiva yah sangAdbhujangAdiva |
vidadhAti vetti sadrisham bhogam cha rogam cha yah ||
yasya samam sa mangalamihAmutrApi martyohashnute ||
He who forsakes all associations with friends like a blind, who is
afraid of associations with the masses like a snake, who sees the
pleasure (bhoga) and ailment (roga) as the same .. that wise man is
known to be liberated always.
YogaVAshishtaSAra, Tattva GyAna Prakarana, Verse 18
So, another pointed highlighted here is that he will avoid all associations with masses.
The commentator (on YogavAshishtaSArah) SwAmi DhireshAnanada comments on the nature and some features of the Jivanmuktah:
Because he sees the world as not true he is like the blind (andha).
Because he knows the inert nature of all the non-self entities like
bodies etc, he is Jadavat (inert).
Since he resides in a state which is inexplicable (anirvachya pAda),
he is mukavat (dumb).
Since he wants to avoid association of all sorts, he behaves like a
mad man and hence is Unmattavat.
RAgadveshabhayAdinAmanurupam charannapi |
sa jivanmukta ucyate ||
Who, although is clear like the Akasha from the inside, shows from
outside, attraction towards food etc, anger towards the wicked, and
fear (towards snakes, tigers etc) is known to be a Jivanmukta.
Laghu YogavAshita 5.93
Symptoms from the Tantras:
I'm using KulArnava Tantram. In chapter 9 of this scripture, Lord Shiva describes the features of the Yogis who have attained self-realization. They are known as the Kula-Yogis in the text.
Yogino vividhairveshairnarAnAm hitakArinah |
Acting in a way that is beneficial to the human beings, these Yogis move about in different
forms, always concealing their true nature. 66
Sakrinnai-vAtma-vijyAnam kshapayanti kuleswari |
O Goddess of the Kulas, they are never detached from the Knowledge of
the Self but amongst the masses, they behave like a mad, a dumb or an
inert person. (67)
AlakshyA hi yathA loke vyomni chandrArkayorgatihi |
grahAnAncha tathaiva kulayoginAm ||
In this world, the movement of the Kula Yogis are unnoticed (that is their real movement is hidden from us) just as
the movements of the sun, the moon and the stars in sky are unnoticed.
Asanta iva bhAshante charantyagyA iva priye |
drishyante kulayoga-vishAradAh ||
O Beloved -- The Kula Yogis speak like the bad people, roam like the
idiots (ignorant) and appear as cheats (to others). (70)
Muktohapi vAlavat kriret kulesho jada-vaccharet |
Vadenn-unmatta-vavidvAna kuloyogi ||
O Great Goddess --- although the Kulayogi is liberated, he plays like
a child, behaves like an inert and talks like a mad man. (72)
YathA hasati lokahayam jugupsati cha kutsati |
Vilokya durato yAti
tathA yogi pravartate ||
The Yogis must behave in a manner so that people laugh at them, despise them, censure them and stay away from them. (73)
So, in short, it is NOT POSSIBLE to recognize a true Jivanmukta. Because, they will always hide their true nature for sure. Moreover, their movements are also concealed from us.