Wanted on murder and corruption charges, Fujimori fled Peru in 2000 after a massive corruption scandal ended his 10-year rule.
"Fujimori has given us the job of defending him with his conviction that he will return to present his candidacy," Cesar Nakazaki, Fujimori's lawyer, said.
"Fujimori will be in Peru by the end of this year, definitely," he added.
Candidates for next April's vote must register by the end of the year to be in the running for the presidency.
Peru's government, which is seeking Fujimori's extradition and may take its case to the International Court of Justice in The Hague, has dismissed re-election plans as a sham.
Nakazaki said he did not expect to end all 20 trials by the end of the year, but rather to show that Peru's justice system did not allow Fujimori a proper defence team since he fled the country.
He said under Peruvian law, that would be enough to annul the cases and allow Fujimori to run for president.
Fujimori says he is innocent of all charges against him.