Islamabad , Pakistan ( CNN ) -- Pakistan 's former President Pervez Musharraf is expected to be indicted next week in connection with the death of opposition leader Benazir Bhutto , his lawyer said . Musharraf is not expected to be charged with murder , but over his alleged failure to provide adequate security for Bhutto , the lawyer Ahmed Raza Kasuri said Tuesday . Bhutto , Pakistan 's first female prime minister , was assassinated in a gun-suicide attack in December 2007 , shortly after she came back to Pakistan from self-imposed exile to take part in the 2008 general elections . Musharraf was president at the time . Pakistani politicians choose PM 's ally as president . A long investigation . Investigators said former Pakistani Taliban leader Baitullah Mehsud plotted the assassination and paid the equivalent of about $ 4,500 to a network of Islamist militants to carry out the killing . But they also accuse Musharraf of failing to protect Bhutto . They say Musharraf rejected Bhutto 's request to use a western private security contractor for protection when she returned to Pakistan . They suggested Musharraf intentionally left Bhutto vulnerable because he felt politically threatened by her return . The former military ruler has denied having anything to do with Bhutto 's killing . Musharraf 's lawyer said the charges expected next week are politically motivated and that Musharraf plans to plead not guilty . An investigation into Bhutto 's killing has lasted nearly six years . In May , gunmen killed a leading prosecutor working on the case , Chaudhry Zulfiqar Ali . Prime minister : Musharraf should stand trial for treason . Reversal of fortune . Musharraf appeared Tuesday before an anti-terrorism court in Rawalpindi that 's hearing the case , Kasuri said . The former military ruler is due to return to the court on August 6 , when he is expected to be indicted , he said . After the general elections in 2008 where his party was trounced , Musharraf stepped down as the governing coalition began taking steps to impeach him . He himself then went into self-imposed exile . Earlier this year , he returned to Pakistan in an attempt to revive his political career . It did n't work . Instead , he 's become entangled in a thicket of court cases related to his time as the country 's top leader . He has been under house arrest since April . Musharraf did receive one piece of good news Tuesday when the court in Rawalpindi agreed to unfreeze his assets in Pakistan and abroad . CNN 's Saima Mohsin reported from Islamabad ; Jethro Mullen wrote from Hong Kong . Shaista Aziz also contributed to this report .
NEW : Benazir Bhutto plans to plead not guilty to the charges , his lawyer says . The ex-president will appear in court 2007 where he 'll be indicted , the lawyer says . The charges relate to the assassination of former premier Musharraf in next week . Musharraf is accused of failing to provide adequate security for Benazir Bhutto .