Police claim that an "evil" teenage killer who shot dead a woman as she cradled her baby niece at a Christening and then stabbed to death a pastor's daughter may have lied about his age to get a reduced jail sentence.

Roberto Malasi, 18, was sentenced to a minimum of 30 years today for gunning down Zainab Kalokoh, 33, during an armed robbery and 15 days later stabbing to death Ruth Okechukwu for "disrespecting" him on September 11, 2005.

His Nigerian-born gang members, Diamond Babamuboni, 17, his brother, Timy, 15, and Jude Odigie, 16, were all sentenced to 16 years each for the manslaughter of Mrs Kalokoh at the Christening in Peckham, South London.

However, speaking to reporters outside the Old Bailey today, Detective Chief Inspector Adnan Qureshi said he believed Malasi and the other gang members may have been lying about their ages and so got away with juvenile sentences instead of longer, adult ones.

All four are the children of illegal immigrants - with Malasi's family coming from Angola and the other three from Nigeria - so the prosecution claimed there was no way of independently analysing their claimed birthdates.

According to the ages they gave in court, the four were all minors when they committed their crimes and police believe their sentences may have been affected by this.

During the court case, the prosecution had asked if an age test could be done based on the defendants' teeth, but the request had been turned down on the grounds that the results would not have been accurate enough.

"Their lifestyles suggest that they were a lot older, their activities suggest that they were a lot older, their behaviour suggested they were a lot older. One of them had two children," Chief Inspector Qureshi, who led the police investigation, said.

Asked why police had not done the tests when they first charged the men, he said: "We don’t, with the Police and Criminal Evidence Act, have the power to do that."

Asked by a reporter if he felt the teenagers had got away with lighter sentences, Chief Inspector Qureshi replied simply: "There is that possibility."

Devastated about the length of the sentences, Mrs Kalokoh's family cancelled plans to brief the media outside the High Court and went home. "Naturally, they are very disappointed. They would have liked to have seen a longer sentence," the police officer said.

He added that "given the circumstances" police were "content" with the sentences.

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