Goofs

During the interview with the computer tech immediately after the flashback with the IBM tech, he reveals he deleted a couple of files. 2 of them, named "LYLE" and "ERIK," were still present in the flashback with the IBM tech. Moreover, his typing doesn't at all match what's on screen (the tech is supposedly typing commands, yet the command line reveals someone is simply hitting the up arrow to previously typed commands).

When the tech is explaining how big a 54k file was, he said "pastrami and rye with a side of coleslaw and hold the pickles, that's 29k" is absolute gibberish. Due to the absolute minimum amount of formatting and meta data stored in files at the time, 54k was more than sufficient for a full will. It's still possible with modern word processors to have files that small, again by reducing the amount of formatting, which would be entirely unnecessary in a will. Just to show how far off that is, the words "pastrami and rye with a side of coleslaw and hold the pickles" typed into the Notepad word processor and saved as a .txt file, with an ANSI encoding, making it very close to the same file format and ASCII encoding used by DOS, is 61 bytes or .061K. Considering that DOS used a lot less meta data than Windows 10 does, that text would have probably been around 30 bytes.

Detective Linehan finds a pair of .22 LR caliber rifles in a closet, saying they were new and had never been fired. There is no way to determine that just by looking at a gun, visually to the naked eye a brand new gun and a gun that hasn't seen a lot use are going to look the same; if a gun has been well cared for it can be very difficult to tell how many rounds have been fired through it. Finding powder residue can indicate a gun was fired recently, but if there is none that could just mean the gun was well cleaned after it was last fired. Plus technically there is no such thing as a gun that has never been fired, after a gun has been manufactured the factory is required to test fire it before shipping it to a retailer to ensure it functions properly. All guns are test fired at least twice, which is why a new gun comes with an envelope containing two spent shell casings, as proof it has been test fired; and some guns are randomly selected for additional test firing.

In the flashback with the IBM tech, it's clear they used a batch file that omitted hiding commands (requiring "@echo off" in the file), and has "rem DOne" as a typo. No one would ever have manually typed "rem" on the command line, as it's specifically used in batch files for processing numerous commands at once. No tech would ever use a batch file to search for file names, nor do the entered commands on the screen suggest he did anything other than list the files in a single directory.

When the detective arrives at the crime scene, the emergency light on the dash was LED, which didn't exist in 1989.

In the flashback with the IBM tech, numerous files have "~1" as the last characters of the filename. One of the features of Windows 95 was long filenames. As a DOS based operating system, Microsoft had to maintain the 8.3 naming scheme for legacy reasons (8 maximum characters for the filename, and 3 for the extension, such as .TXT or .DOC). A file that contained "~1" indicated that inside of Windows 95 (and 98 or ME), the filename was longer than 8 characters. The computer would not have had files named as such in 1989, some 5-6 years before the release of 95.

When the girlfriend shows up, the brother describes some of people around his father as "sketchy" characters -- a term in current usage but not in 1989.