From the Fox TV forensic psychology police-procedural show Lie To Me (Male Investigator is talking to Female Investigator about a suicide note she has decided is fake):
Male Investigator: Let me ask you something: how can you tell if this thing is fake if it's been typed?
Female Investigator: Word choice, repetition, and the use of passive or active voice can tell you a lot about the person who wrote this.
Of course! Passive versus active voice. Why didn't I think of it. That should tell us what we need to know about who wrote the note.
The suicide note they are talking about reads as follows:
I can't live through the hell awaiting me. I simply won't. A person of my stature should know better.
I helped Michelle because of my feelings for her. She begged me to save her, and I was weak.
When she hit that homeless man, I should have let her go to prison for it, but I had the charges dropped.
They'll crucify me. People love it when someone in my position is brought down. I made one mistake with regards to a subordinate, and I'd never hear the end of it. I refuse to give my enemies the satisfaction of seeing me suffer.
The woman investigator goes on to explain her methods:
Female Investigator: Let me show you. "A person of my stature", "someone in my position", "With regards to my subordinate". This is a person who is preoccupied with power and status.
Male Investigator: Power and status, huh? That sounds like the Trevor Addison you were describing earlier.
Female Investigator: It's all about the pronouns. Women, we use a lot more pronouns when we write. I, she, they. Men will typically name the person or thing they're talking about.
Male Investigator: MI: So a woman preoccupied with power and status wrote this?
Female Investigator: Yep.
Forensic psycholinguistics is so easy! Watch for those sex-revealing pronouns, check for that telltale passive (there actually is one in the note — no, two of them, as pointed out in a comment by Astrid below!), and bingo, you got it nailed. A woman obsessed with status wrote it. And you don't need no stinkin' CSI lab.
Naturally, a man would have written the note very differently, naming things rather than using those girly pronouns. I'll get rid of the pronouns (I, she, they, as Female Investigator helpfully reminds us — and notice that she does include the first person singular pronoun!); I'll put in names instead, and I'll convert any girly passives to manly actives as well. For present purposes, let's assume that the man who committed suicide was called Irving:
Irving can't live through the hell awaiting Irving. Irving simply won't. A person of Irving's stature should know better.
Irving helped Michelle because of Irving's feelings for Michelle. Michelle begged Irving to save Michelle, and Irving was weak.
When Michelle hit that homeless man (Gus Diaz), Irving should have let Michelle go to prison for the act in question, but Irving had the district attorney (Sheldon Kramsky) drop the charges.
The relevant person or persons unknown will crucify Irving. People (Bob, Harvey, C.J., Vince the janitor… lots of people) love the resultant situation when people bring down a person in Irving's position. Irving made one mistake with regards to a subordinate (Michelle), and Irving would never hear the end of that mistake. Irving refuses to give Irving's enemies (Bob, Harvey, and many others) the satisfaction of seeing Irving suffer.
That sounds a lot more plausibly male, doesn't it? Female Investigator would not have spotted any fake-maleness in that. Get your grammar right, and you've basically got it made as a suicide-note forger.
[Acknowledgment: Many thanks to Daniel Hougey, who tipped me off about the program (said to be inspired by the feats of real-life emotion-detecting psychologist Paul Ekman) and transcribed the dialog above.]