These days we have more access than ever to information about our favorite celebrities. Experts say in extreme cases this kind of intimacy can make a deranged fan feel like a star is talking directly... See More
These days we have more access than ever to information about our favorite celebrities. Experts say in extreme cases this kind of intimacy can make a deranged fan feel like a star is talking directly to them and that can lead to stalking. Tonight we are going to take a look at this uniquely modern problem starting with a bizarre case of alleged stalking that is playing out today in a new york city courtroom. Here is abc's nick watt. Reporter: Alec baldwin for my money the best baldwin, actually cried in a new york city courtroom this morning as he described his living nightmare. Baldwin, the debonair star of "30 rock" claims he was stalked by this woman, a two-bit canadian actress. I say loud and clear that i am innocent since day one. Reporter: Baldwin claims she would bombard him with 30 text messages a night. Here is one, say I do to me. He says she showed up at his hampton's home, bombarded him with salacious e-mails. Here is a taster dished up in court. I want to feel you, taste you, and make one with you for eternity. I will nourish you with my energy, power, and magic. She offered all this and more, in exchange for a new house in new york and montreal, a new wardrobe, car, and jewels. In one e-mail she states, I want to be your wife. Now. Last year, she was arrested outside baldwin's manhattan home. She claims a misunderstanding she and baldwin were once lovers. You want to go for coffee with closure for your ex-lover. It is 4:00 in the afternoon. Not like I was there unannounced. You announce yourself to somebody you have a relationship with and romance, we have many friend in common. It is normal. Reporter: Alex baldwin denies any relationship and describes his brush with her like something out of a hitchcock movie. Stalking an occupational hazard for today's celebrities on line and in the flesh. Just watch this. Put your hand on the wall. Reporter:4:00 a.M., Those are the gates of miley cyrus' hollywood home. That man 40-year-old jason rivera had a giant red heart around his neck and unhealthy obsession with the 19-year-old singer. I have scissors. Reporter: Rivera found guilty of trespass slapped with a three year restraining order. He is not allowed within 1,000 yard of miley. For the protection celebrities get from the cops and courts they have this woman to thank, rebecca schaeffer rising star in THE 80s PLAYED PATTY ON THE HIT Tv show "my sister sam." Bran doidon is. Back in the days there were no stalking laws in california or anywhere else. Reporter: Rebecca had a stalker, robert bardo. Reporter: Bardo was enraged when he saw schaeffer getting into bed with a man "scenes from a class struggle in beverly hills" classic stalker behavior. How dare she. She is not remaining pure for me. Th put the victim on the pedestal. But once they're rejected it is anger, rage, rejection. Reporter: Bardo tracked her down and showed up at her apartment with a gun. Reporter: He shot rebecca schaeffer dead on her front doorstep. She had to be victim of a homicide in order for us to get message that something need to be done by way of legislation. Reporter: Laws were passed the lapdtalker unit was born which protected the likes of morgan fairchild prey for multiple stalkers who ironically once played a stalking victim in "seduction." Hello? I watched you today? What? Reporter: Once she says a female fan began writing innocent postings on her website. Then started sending card, gifts, and disturbing handwritten letters to her home address. I am going to show up on your doorstep. Fly across the country. You promised me you would pay our bills. You haven't done it. Now I am angry. I was like, uh, it was getting threatening. Reporter: The obsessed fan believed fairchild was her mother. With all the technology that is readily available to any weirdo on the street, you, do get a little concerned about, about your safety, your security. That's where we come in. Part of our job is managing that fear. In addition to managing the case. Madonna suffered nightmares after being stalked by a man named robert hoskins. The thing that makes him dangerous. He is focuseded on madonna as a spirit. He believes the ma dospirit can in h hab y habit. Reporter: He was sentenced to 10 years. Dr. Reid malloy, studies stalking and believes modern celebrity culture may be fueling the problem. The more the magazines humanize the celebrity figure the more it can reduce the space between the stalker and celebrity figure. The internet makes it easier with youtube, twitter, because these stalkers believe that the celebrities are actually talking directly to them. Reporter: This woman stalked brad pitt. Broke into his home. Fed his dogs and slept in his pajamas. These are people who don't have a lot going on in their lives. All of a sudden, they can pull strings and they can make some one afraid of them. Reporter: This man was jailed in 1998 for 25 years after he was caught trying to break into steven spielberg's home armed with a box cult tter, handcuffs and duct tape. He told police he wanted to rape the director. Oftentimes they're living alone. They have typically had unstable work histories. They have not done well. Often times that's because of the psychiatric disorder. Paradoxically they tend to be brighter than average. Reporter: Any way, back to alex baldwin and the woman who apparent leap first met in 2000, he was in canada, shooting a film. Ten years later they had dinner in new york. Baldwin now married to his then girlfriend, says she was asking for acting advice. She claims, they became intimate. Are you a stalker? Did you stalk him? No, I am not. You don't kid yourself a stalker? He maintained a relationship with me while he was with her. Now that's why he created it. Reporter: In court, baldwin vehemently denied. There was ever a sexual relationship. At which point, she screamed really? She then shouted he is leagying to you! Baldwin leaving court, clearly agitated telling a cameraman. I am nick watt for "nightline."
This transcript has been automatically generated and may not be 100% accurate.