According to Paragraph 391 of the Immigration Rules in the case of a person who has been deported following conviction for a criminal offence, the continuation of a Deportation Order against that person will be the proper course:
(a) in the case of a conviction for an offence for which the person was sentenced to a period of imprisonment of less than 4 years, unless 10 years have elapsed since the making of the Deportation Order when, if an application for revocation is received, consideration will be given on a case-by-case basis as to whether the Deportation Order should be maintained, or
(b) in the case of a conviction for an offence for which the person was sentenced to a period of imprisonment of at least 4 years, at any time.
However, it is worth to emphasize some particular circumstances and rely on some relevant jurisprudential doctrine applied in similar cases brought to the European Court of Human Rights. It firstly comes to mind Üner v. the Netherlands, 46410/99 which was published on 18th October 2006 and inspired the subsequent doctrine related to the interpretation of the Deportation Order policy.
In that case, the European Court of Human Rights judges shed light on the decision criteria for a deportation order revocation.
36. Recommendation Rec(2000)15 states, inter alia:
“4. As regards the protection against expulsion
a. Any decision on expulsion of a long-term immigrant should take account, having due regard to the principle of proportionality and in the light of the European Court of Human Rights' constant case-law, of the following criteria:
the personal behaviour of the immigrant;
the duration of residence;
the consequences for both the immigrant and his or her family;
existing links of the immigrant and his or her family to his or her country of origin.
b. In application of the principle of proportionality as stated in Paragraph 4.a, member states should duly take into consideration the length or type of residence in relation to the seriousness of the crime committed by the long-term immigrant. More particularly, member states may provide that a long-term immigrant should not be expelled:
after five years of residence, except in the case of a conviction for a criminal offence where sentenced to in excess of two years' imprisonment without suspension;
after ten years of residence, except in the case of a conviction for a criminal offence where sentenced to in excess of five years of imprisonment without suspension.
after twenty years of residence, a long-term immigrant should no longer be expellable.
In the light of this, it seems essential assessing the application on a case-by-case basis and putting an accent on the principle of proportionality. Although the Applicant could be fairly sentenced due to the commission of a juvenile mistake, there could be some attenuating circumstances to take into account.
Another pertinent case law of the European Court of Human Rights is Maslov v Austria ECHR (1638/03, Bailii,  ECHR 221, Bailii,  ECHR 224) which was published on 2007 and defined the criteria which must be considered in order to issue a deportation order as follows:
'In a case like the present one, where the person to be expelled is a young adult who has not yet founded a family of his own, the relevant criteria are:
the nature and seriousness of the offence committed by the applicant;
the length of the applicant’s stay in the country from which he or she is to be expelled;
the time elapsed since the offence was committed and the applicant’s conduct during that period;
the solidity of social, cultural and family ties with the host country and with the country of destination.
The Court would also clarify that the age of the person concerned can play a role when applying some of the above criteria. For instance, when assessing the nature and seriousness of the offences committed by an applicant, it has to be taken into account whether he or she committed them as a juvenile or as an adult (see, for instance, Moustaquim v. Belgium, judgment of 18 February 1991, Series A no.193, p.19, ss 44, and Radovanovic v. Austria, no. 42703/98, ss 35, 22 April 2004).'
Ultimately, the seriousness of the crime should be measured by considering the age of the person at the time of the offence commission, the length of the Applicant's stay in the country and the time elapsed since the offence was committed, as well as the solidity of social, cultural and family ties with the host country and with the country of destination.