Goofs

Toward the end when Brian jumps out the window and the possessed people outside come towards him, it is clearly dawn and light outside. Shortly after, when the possessed is defeated and the mirror is broken by the priest, you can see them dispersing while it is night outside. Then Walter jumps out to get help and it is night as well. The next scene shows Walter with a blanket around him and is dawn again.

We see the new moon very close to the sun (though showing far too much crescent for such a small angle). A few scenes later, Brian Marsh is looking at a full moon, then a few more scenes later, we see the new moon again near the sun. That night, we see the full moon again.

When Lisa gets into bed, her shoes are off. However, after she becomes possessed and is walking around, her shoes are back on.

Position of Wyndham's head changes between shots when he is shown dead.

When Walter is being pulled through the wall, there are discrepancies over how much of his body is seen on either side of the wall.

(at around 38 mins) The student radiologist Susan Cabot says she has been "carbon dating the corrosion on the lid" of the cylinder, and "we're talking about 7 million years". Carbon dating is used to determine the age of materials, usually organic, containing carbon, not metal corrosion substances, and is only useful for about 60,000 years.

(at around 12 mins) In the beginning of the movie the Priest tells Dr. Birack that the Catholic Church containing the demonic fluid, located in Los Angeles, was built in the 1500s by Spanish missionaries. The Spanish did not colonize California with missions until 1769, with the founding of San Diego by the explorer-missionary Fray Junipero Serra. The mission where filming took place, Mission San Fernando Rey de España, was not founded until 1797.

At the beginning of the film Dr. Birack looks up and sees the Sun and crescent Moon together, one above the other. This is impossible as in order for a crescent moon to exist the Earth would need to be between the Sun and Moon which is what cast a shadow on it.

(at around 1h 29 mins) After Walter crawls through the hole in the closet with "possessed" Lisa in tow, they're both in the other room with Prof. Birak, all standing up. You can see the obvious doubling of "short Lisa" by a stuntman - she's suddenly much bigger and taller than the two other men.

(at around 60 mins) When Lisa is typing "I Live!" over and over on the computer keyboard, her fingers in no way match the letters being typed on the screen.

(at around 56 mins) When Susan climbed onto Lisa's bed and sprayed the liquid "evil" into Lisa's mouth, the liquid was obviously sprayed from a tube behind Susan's mouth instead of from inside it.

To throw an axe like the priest at the end did, with one hand, would take a LOT of strength, and even if he could do it, the way he thrown it, it wouldn't hit the mirror like it was shown.

When Birack first visits the church with the Priest, he is told the former Guardian priest unlocked the door every day, but it is implied that he was the only visitor and the only person who knew about the cellar and its' contents. As they descend the steps, the cellar is full of literally hundreds of lit candles, some in almost inaccessible places high up on the walls. Who lit them all and who replaces them when burned out

Throughout the film, Brian Marsh's mustache is uneven. The right side is lower down on his face than the left.

When the Priest is sending a letter to Dr Birack at the start of the film he is sending the letter to an address in Los Angeles, but puts the zip code for Los Angeles as 98005. 98005 is the zip code for King County and its surrounding areas in the state of Washington. Zip codes in Los Angeles start with either 90 or 91.

Giving Calder the last rites, the priest says "absolvae" instead of "absolvo".