Hundreds of cases involving young immigrants could be reviewed following a Supreme Court decision allowing judges to determine the age of applicants for the purposes of accommodation and other services provided by local authorities.

Ruling in R (on the application of A) v London Borough of Croydon and R (on the application of M) v London Borough of Lambeth [2009] UKSC 8, the Supreme Court held in a unanimous decision that determining a person?s age was a matter of objective fact that judges could carry out.

The two asylum seekers in the case, A from Afghanistan and M from Libya, claimed they were under 18 but were assessed by the respondent local authorities as being adults.

Lady Hale said whether an applicant was ?a child? under the Children Act 1989 was not the same as whether he was ?a child in need?.

?The Act does draw a distinction between a ?child? and a ?child in need? and even does so in terms which suggest that they are two different kinds of question,? she said.

However, she made it clear that such a decision rested with local authorities and that it was ?only if this remains disputed that the court may have to intervene?.

According to Lady Hale, judicial review proceedings remained the appropriate route for such challenges.

The case will now go back to the High Court for a hearing likely to involve days of evidence.

According to A?s solicitor, Hugh Purkiss, it is one of about a hundred live court cases addressing similar issues, which, if all require lengthy determinations of fact, could clog up the courts.

Hundreds more could follow as undisputed assessments are likely to be reopened in the wake of the court?s ruling.

Victoria Pogge van Strandmann, a solicitor specialising in public law at Fisher Meredith, confirmed that the number of age assessments had increased dramatically in recent years but that there was little public awareness, as the majority of cases did not reach the courts.

Now, she said, this number was likely to increase again as lawyers would be reviewing cases, particularly where negative advice had been given.

But assessment of facts as part of judicial review proceedings would be ?fresh territory? for judges, Purkiss said.

?The general feeling between counsels and solicitors is that that it?s going to be a hybrid where you challenge a local authority?s decision on public law principles while also challenging it on a private law basis asking the court to look at the factual evidence,? he said.

Unusual as this approach was, Purkiss said, it would not be entirely new as there had been previous cases where public law cases involved considerations of fact. He cited the case of TK [2008] EWCA Civ 103, last year, where a five-day fact-finding hearing took place in the course of family law proceedings.

Pogge van Strandmann agreed that this ?hybrid? approach was ?a big turnaround? as it was unusual for the Administrative Court to determine questions of fact and that lengthy evidence-gathering hearings could lead to congestion in court.

?Courts are adaptable, but while an average judicial review hearing takes about a day, it will take significantly longer if the court is required to consider evidence,? she said. ?And this will put pressure on the Administrative Court, which, at times, is already struggling to expedite cases that need speedy resolution?.

One possible solution would be the creation of a specific tribunal within the Tribunals Service, whose jurisdiction would be to hear age assessment appeals. Purkiss would support this option though he agrees there would be costs implications.

The parties in the case now have 14 days to make written submissions as to how they wish the case to proceed and about costs.