He was hired by defence lawyers to look into Madam Valli's claims that she was traumatised during a forced exorcism at the Novena Church on Aug 10, 2004.
Madam Valli, 52, is suing the Redemptorist Order that runs the church, two priests and six churchgoers.
The defence team says the video footage by Mr De Silva proves that Madam Valli is not as distressed as she claims.
They contend that she is faking symptoms of post-traumatic stress disorder to get money from the church.
Her two doctors were shown the video, but they stood by their diagnoses.
Madam Valli's sister is expected to take the stand today for the defendants.