He represented Waterloo North in the Legislative Assembly of Ontario as a Conservative member in 1898 and again from 1903 to 1912.
He was born in Hawkesville, Canada West, the son of William Lackner, a German immigrant.
Lackner was licensed as a physician in 1876 and set up practice in Berlin (later Kitchener).
Lackner also served as medical health officer for Berlin.
He resigned his seat in 1912 when he was named sheriff for Waterloo County; he served in that post until his death in 1925.