A convict serving a life sentence for five murders and thought to be a friend of the notorious Palaiocostas brothers has escaped from custody, authorities said yesterday after confirming that Michalis Makriyiannis had not returned from a prison furlough. Authorities said that Makriyiannis had been due to return to Alikarnassos jail in Crete on Monday after a five-day leave. It is customary to give prisoners a two-day extension before they are deemed to be fugitives, jail chiefs said. Makriyiannis was convicted of murdering five people between 1990 and 1993. He was also found guilty of three attempted murders and several armed robberies. He was arrested in December 1994, several months after he was involved in a shootout with police officers. Authorities said they believe that Makriyiannis is a friend of wanted criminals Vassilis and Nikos Palaiocostas. Nikos, who has eluded arrest for some 16 years, allegedly helped his brother escape from Korydallos Prison in a helicopter three months ago.