The test of vulnerability pursuant to Housing Act 1996,s.189 has recently been clarified by the Supreme Court: Hotak v Southwark LBC; Kanu v Southwark LBC; Johnson v Solihull MBC  UKSC:
(a) In assessing whether an applicant is vulnerable, an authority must pay close attention to the particular circumstances of the applicant .
(b) Certain expressions commonly used in decision letters, e.g. “street homeless” and “fend for oneself”, are problematic and should be avoided [40-42]. Whether the applicant can fend for himself is not the statutory test. The expression “street homeless” can cover a number of different situations.
(c) In order to decide whether an applicant falls within s.189(1)(c), an authority should compare him with an ordinary person if made homeless, not an ordinary actual homeless person 
(d) the test is whether the Appellant would be significantly more vulnerable than an ordinary person who is made homeless.
Where there is more than one condition the authority must consider the cumulative impact of the various conditions on the applicant: Crossley v Westminster City Council  HLR 26,CA ; Homelessness Code of Guidance, para 10.14.
There need not be actual injury or detriment. An increase in the risk of injury or other harm is itself a detriment: Griffin v City of Westminster  EWCA Civ 108,CA.
Any rejection of medical evidence by the authority must be (expressly) reasoned (R v Wandsworth LBC, ex p. Dodia (1997) 30 HLR 562 at 565 QBD).
The Homelessness Code of Guidance –June 2006 (“The Code”) states at paragraph 10.14: “The applicant’s vulnerability must be assessed on the basis that he or she is or will become homeless, and not on his or her ability to fend for him or herself while still housed”. See also Osmani v Camden LBC  EWCA Civ 1706;  HLR 22.