information to build >> reporter: after controversy in the early 2000s, aclu legal director mark silverstein says denver police agreed to stop collecting information on law-abiding citizens expressing their views. now he says the department has the technology to quietly go back on its word. >> we just don't know how the denver police department is using or intends to use this geofedia helps them track social media posts coming from a certain area like a protest. last month an online publication reported denver acquired the tool without making the purchase public. aclu wants to see the terms police search. >> we think somebody might be more hesitant to attend a rally, to go to a demonstration, to sign a petition if they know that doing so is going to make them the target of police attention. >> reporter: denver's department of cloud-based platform to identify open source posts that may assist with the prevention of violent acts and to assist with identifying criminal activity. the platform also allows the department the ability to gain on awareness of events which could impact public safety.

. >> reporter: mark silverstein filed a class action suit then. he's curious if he'll have to do the same with denver's newest investigative software restricts the use of this software? we need to know what's going on. >> reporter: the purchase was submitted in march approved under the pretense that it had helped investigations in both the boston marathon bombing and shootings. the gray area comes on what grounds can police begin to target certain people on social media? >> the focus right now appears to be to require reasonable suspicion in order to use surveillance of the social media sites of political is it appropriate to identify certain people as threats simply by searching a political movement's hashtag such as black lives matter? the 2002 ruling would suggest no. >> i would hope that there would be a detailed policy spelling out what limits will be placed on denver police officers. >> reporter: silverstein and 9news are awaiting the release of that policy from police. denver police released a statement today to 9news saying in part they us

. >> reporter: after controversy director mark silverstein says denver police agreed to stop collecting information on law-abiding citizens expressing their views. now he says the department has the technology to quietly go back on its word. >> we just don't know how the denver police department is using or intends to use this software. >> reporter: the software, geofedia helps them track social media posts coming from a certain area like a protest. last month reported denver acquired the tool without making the purchase public. aclu wants to see the terms police search. >> we think somebody might be more hesitant to attend a rally, to go to a demonstration, to sign a petition if they know that doing so is going to make them the target of police attention. >> reporter: denver's department of public safety writes, police use the cloud-based platform to identify open source posts that may identifying criminal activity. the platform also allows the department the ability to gain on awareness of events which could impact public safety. >> the aclu says it also wants to see whether the depar

. >> reporter: mark silverstein filed a class action suit then. do the same with denver's newest investigative software now. >> do they have a policy that restricts the use of this software? we need to know what's going on. >> reporter: the purchase was submitted in march approved under the pretense that it had helped investigations in both the boston marathon bombing and shootings. the gray area comes on what grounds can police begin to target certain people on social media? >> the focus right now appears to be to require reasonable suspicion in media sites of political organizations. >> reporter: in other words, is it appropriate to identify certain people as threats simply by searching a political movement's hashtag such as black lives matter? the 2002 ruling would suggest no. >> i would hope that there would be a detailed policy spelling out what limits will be placed on denver police officers. >> reporter: silverstein and 9news are awaiting the release in part they use the software to "identify open source posts that may assist with the preve