For example, if the defendant, under improper questioning, gives information to the police about a witness who could vouch for him, and the police consequently question that witness and obtain evidence incriminating the defendant, how should the court decide whether the incriminating evidence is admissible? Facts like this were considered in HM Advocate v P (Scotland)  UKSC 44 (6 October 2011). This is a companion case to that considered in my note yesterday.
The position in domestic Scots law is that if the evidence could be led without reference to the improperly obtained evidence it would not be treated as inadmissible by reason of it having been found as a consequence of the improperly obtained evidence: Lord Hope at 17, citing Lawrie v Muir 1950 JC 19. Similarly, in England and Wales under s 76(4) and 78(1) of PACE 1978 all the circumstances must be considered and the consequential evidence is not invariably excluded: at 18.
As far as Strasbourg jurisprudence went, there was no definitive decision but guidance could be obtained from Gäfgen v Germany (2011) 52 ECHR 1 (noted here on 3 July 2008, Chamber, and Grand Chamber on 25 June 2010): Lord Hope at 22. No rule of automatic exclusion of such consequential evidence has been established 23.
The Supreme Court found some assistance from Canada: Thomson Newspapers Ltd v Canada (Director of Investigation and Research)  1 SCR 425, where the distinction was made between evidence created by impropriety, and evidence that may have gone undetected but for the impropriety but which nevertheless existed independently.
This was consistent with the conclusion Lord Brown reached 27:
See also the attenuation approach in R v Wittwer (discussed here 6 June 2008), and occasions where a consequential link may be dispensed with but evidence nevertheless excluded: R v Ogertschnig (discussed here 26 October 2008). Improprieties may taint evidence without there being a consequential link, and as the present case shows, improprieties may be irrelevant notwithstanding such a link.