When Katherine meets Phillip outside San Quentin after his release, the closeups of her were obviously shot outside, while his closeups, with a picture of the prison on a back-screen behind him, were obviously shot in the studio.
In the prologue, Phillip Stewart is shown in San Quentin State Prison, serving a sentence for an involuntary manslaughter conviction. San Quentin was and is a maximum security institution intended to house the worst offenders in the California penal system, and anyone convicted of a relatively minor felony (such as involuntary manslaughter) would be sent elsewhere.
When Phillip Stewart redeems an item from a pawn shop, he asks if the shopkeeper has anything to wrap it, and the pawnbroker says he has newspaper. The paper he gives Stewart appears blank. However, when Stewart unwraps the parcel later, revealing a music box, during the camera's closeup as he removes its false bottom, faint writing can be seen on the paper, showing that it may actually be some sort of newspaper.
A scene shot in a taxi shows back projection of the San Francisco street scene outside. The street is on a hill and the buildings diverge noticeably from the perpendicular, but the taxi interior is completely level and, therefore, not parallel to the street.
Multiple witnesses who watched the lighted numerals above the door testify that a business elevator descended to lobby level without stopping. But it is later proven that the elevator made one stop.
Several times Perry pronounces the port city San Pedro as "San Paydro." Any Angelino would use the local pronunciation, as does Paul, "San Peedro."