For its investigation into rape kit destruction, CNN examined thousands of records from sources that included federal and local law enforcement agencies, courts and The National Registry of Exonerations. In addition, reporters interviewed and consulted more than 50 experts in policing, law, forensic science and trauma. The goal was to determine whether rape kits were improperly destroyed, where and why.

About the data

We began collecting data for this project in May 2016 by surveying local law enforcement agencies from 49 states and the District of Columbia about whether they had destroyed any sexual assault kits, or rape kits, since January 1, 2010. We chose those jurisdictions by looking at data from the FBI Uniform Crime Reporting program on cities in each state with the largest population, the highest raw number of rape reports, and the highest number of rape reports per capita in 2014 (the most recent data available at the time). We surveyed three agencies in most states and five in those that appeared, based on published accounts, to have no statute of limitations on rape or sexual assault. In the latter, we used an additional criterion to select the additional jurisdictions: the largest cities, by reported rapes per capita, with populations larger than 5,000. Our initial sample did not include Hawaii because the FBI did not have 2014 rape data for agencies in that state.

We used these measures to focus on places where sex crimes were known to have occurred and rape kits were reasonably likely to have been collected. By including some cities based on their reported rape rate and not simply on size or raw count of reported rapes, we were able to include in our sample agencies in smaller jurisdictions to see how they handled rape kit evidence.

Our initial process identified 186 cities and agencies. When police departments referred CNN to other law enforcement agencies, such as county sheriff’s departments or state police, we followed up with requests to those agencies. Interviews and other sources, such as local news reports about kit destruction, led us to seek data from 14 additional agencies. Overall, we requested data from 207 law enforcement agencies.

Four agencies either refused to provide information or did not respond to requests. The others split almost evenly: 102 agencies in 43 states said they had not destroyed kits; 99 agencies in 47 states reported destroying at least one rape kit since 2010.

Building our database

We spent months sifting through agencies’ responses and building a database of destroyed rape kits. Some agencies could not or refused to provide records for the requested time period. One department told CNN the cost of fulfilling the public records request would be $143,133.50; another police department asked for $43,715. After some negotiation, the former provided partial data for $2.25 and the latter for less than $500.

Records from many agencies contained errors. Where necessary, we sought additional information from them to identify and remove duplicate entries and complete, confirm or correct information about kits, including:

Whether the evidence was a rape kit or something else, such as victim’s clothing or bedding;

Whether kits were actually destroyed (as opposed to transferred to another agency);

Whether each kit was collected from an adult or minor victim;

Whether each kit was submitted to a lab for testing;

When the agency took custody of each kit;

When the agency destroyed each kit;

The status or disposition of each case;

What sex offense was alleged, investigated, presented for prosecution or charged; and

Why the agency destroyed each kit.

Altogether, we built an initial data set of more than 7,000 destroyed rape kits from 102 agencies in 43 states. This included two kinds of rape kits that we excluded from our analysis: “Anonymous kits,” which are collected when a victim completes a sexual assault exam but does not report the crime to police, and “suspect kits,” which are collected from suspects to match their DNA to evidence from a crime scene or victim’s rape kit.

Byproduct evidence

When labs analyze rape kits for DNA evidence, they extract DNA from samples, such as swabs, in the kit. Scientists then make hundreds of thousands of DNA copies, known as amplified product, that they analyze to try and identify whom the original DNA came from. Some crime labs or law enforcement agencies keep these DNA extracts, amplified product or samples from rape kits that are submitted for testing, such as cuttings from swabs or hair collected during the rape exam which could contain DNA evidence.

To identify tested kits in which samples, DNA extracts or amplified product might have been kept, we interviewed state lab directors and law enforcement officials about their retention procedures and reviewed property and chain-of-custody records. We excluded those kits from our analysis because that evidence could help prosecutors bring charges.

Improper destruction

We consulted more than 50 experts in policing, forensics and the law while reporting this project. At CNN’s request, at least a dozen of those experts reviewed investigative case files. They identified mistakes law enforcement made in those cases and taught reporters to discern whether other cases were conducted in a thorough and trauma-informed way.

While some experts said rape kits should never be destroyed, a handful said the destruction could be permissible under certain circumstances, such as after the time limitation on prosecuting a crime expired, after cases were resolved in court or when an investigation demonstrated that a crime had not occurred.

The most egregious destruction, experts told us, happened in cases in which crimes could still be solved or be prosecuted, either because there was no time limit on when prosecutors could file charges or because the time limit had not yet expired.

To find those cases, we calculated the age of each kit based on when police said they received and destroyed it. We used those estimates to identify which agencies reported destroying kits in less than two years and at least 10 kits in less than one year.

We made additional public records requests to obtain the investigative reports for cases from those agencies, which provided more information about the circumstances in which kits were destroyed. Because we made these requests based on the data we had at the time, we did not request documents for cases from two agencies whose data we later obtained that met these criteria.

CNN also requested several police reports for cases that police data suggested were open when the kits were destroyed. We also requested case files when the victim was a minor, when experts said the statute of limitations on a crime often would not have started ticking until the victim reached adulthood.

Altogether, we examined narrative reports for 1,444 cases in which rape kits were destroyed since 2010.

To identify cases that experts said may still have been able to be prosecuted, we read the police reports and focused on cases we called “unsolved,” meaning cases police described as open or in which investigators never identified or never apprehended a suspect; prosecutors declined to charge a suspect; victims decided not to prosecute after reporting a crime or refused to cooperate with police; or an investigation stopped because leads ran dry.

Some agencies challenged our use of the term “unsolved” or “open” to describe some of these cases, which experts told us law enforcement traditionally defines more narrowly as cases in which police have not identified a suspect. Many of their kits, some agencies said, were destroyed in cases that were “closed,” but could be re-opened if new leads emerged or a victim or prosecutor changed their mind. However, experts said police should have instead maintained that evidence for as long as a prosecution could be made.

We excluded cases that ended in an arrest, went to a court, and in cases in which police determined no crime occurred or law enforcement took custody of rape kits during investigations into suspicious incidents and deaths. We also excluded cases in which we could not determine the outcome or when a suspect’s death ended authorities’ chance to prosecute the crime.

We identified 743 kits from “unsolved” cases. They came from five categories that we developed using keywords or by evaluating the facts in each case:

Open: Cases that police described as “open,” “inactive,” “suspended” or “pending,” or that police said could be reopened if new leads emerged;

Cases that police described as “open,” “inactive,” “suspended” or “pending,” or that police said could be reopened if new leads emerged; Victim Uncooperative: Cases in which police closed an investigation because, authorities wrote, victims had stopped “cooperating” or became “uncooperative;”

Cases in which police closed an investigation because, authorities wrote, victims had stopped “cooperating” or became “uncooperative;” Victim Declined Prosecution: Cases in which police closed an investigation or charges were not filed because police said the victim declined to move forward, either verbally or by signing paperwork to that effect;

Cases in which police closed an investigation or charges were not filed because police said the victim declined to move forward, either verbally or by signing paperwork to that effect; Prosecutor Declined: Cases in which police closed an investigation after a prosecutor declined to file charges in the case; and

Cases in which police closed an investigation after a prosecutor declined to file charges in the case; and Insufficient Evidence: Cases police closed because of a lack of leads, an inability to reach the victim or “insufficient” evidence.

Determining statutes of limitations

Determining what time limit, if any, exists on prosecuting a crime can be complicated. Laws vary by state and over time. Making precise determinations can require knowing several factors, such as where and when the crime occurred, the specific offense, when the crime was reported, the victim and suspect’s ages, whether DNA evidence existed or could identify a suspect, and whether a suspect was known but out of law enforcement’s reach.

To identify kits destroyed in crimes that could still be prosecuted, we looked at the offense authorities listed in each case. In some cases where the offense was unclear, we consulted legal experts to help determine the most likely offense. We were able to identify an offense for 736 of the 743 kits destroyed in unsolved cases. (We excluded non-sex crimes and attempted crimes.)

We then grouped these kits by state and consulted sources such as Justia, LexisNexis and state legislatures’ websites to research the statute of limitations on the crimes when they were committed.

In jurisdictions with few kits, we researched the statute of limitations for each kit.

In states with many kits spanning several years, we grouped kits by year and focused on years with the most kits. This allowed us to analyze a bulk of cases without researching each iteration of each state’s laws. In Washington, for example, we only attempted to determine the statute of limitations on cases from 2008, capturing 48, or almost two-thirds, of the 73 kits destroyed in unsolved cases.

We took three approaches to ensure CNN applied the shortest — and most conservative — possible statute of limitations:

When departments’ records named a specific offense using its statute code (for example, “Idaho Code § 18-6101”), we researched and applied the statute of limitations for the specific crime.

When records provided a general offense, such as “sexual offense” or “sexual assault,” but not enough information to conclusively pinpoint the statute of limitations, we assumed the least severe version of the named crime. In New Mexico, for example, many kits were tied to crimes that police records described as “criminal sexual contact,” which could be a felony or a misdemeanor. If police did not specify which, we assumed the lesser crime — the misdemeanor — which would carry a shorter statute of limitations.

When records only indicated whether a crime was a felony or a misdemeanor, we applied the minimum time limit on prosecuting felonies or misdemeanors in that state.

In some states, certain conditions could eliminate or extend the time limit on prosecuting crimes or “toll” that time limit, meaning delay its implementation. In those cases, and where the relevant facts were unknown, we erred on the conservative side by applying the shortest possible statute of limitations. For example:

When the time limit on prosecuting a crime could be extended because a suspect’s location was unknown or was out of authorities’ reach (because they left the state, for example), we assumed the suspect was present and their location was known to authorities.

When the time limit on prosecuting a crime could be extended or delayed until a suspect was identified, we assumed the suspect’s identity was known to authorities immediately.

When the time limit on prosecuting a crime could be extended or eliminated if the crime was reported to police within a certain time, we assumed crimes were reported after that time had ended. In Florida, for example, the statute of limitations on sexual battery typically expired after three years, unless the crime was reported within 72 hours. Then, no statute of limitations applied. In cases where we didn’t know when a crime was reported, we assumed it was reported after 72 hours and applied the shorter statute of limitations: three years.

Some states also extended or eliminated the time limit on prosecuting crimes when a suspect is identified through DNA testing. In those cases, we determined that untested kits were destroyed while their crimes could still be prosecuted because, by failing to test the kit, police forfeited an opportunity to extend the time to prosecute.

Altogether, we analyzed 522 of the 743 kits destroyed in unsolved cases to determine whether the kits were destroyed before the statutes of limitations expired. To focus on recent investigations, we limited our analysis to cases opened since 2005, when the International Association of Chiefs of Police issued guidelines for investigating sexual assaults.

Our estimate of improperly destroyed kits may be an undercount; some cases we examined could have carried longer statutes of limitations than we were able to determine or even no statute of limitations at all.

Vetting our findings and data

To vet our findings, we consulted with legal experts, including criminal procedure law experts and practicing criminal attorneys, in the 15 states where kits were improperly destroyed.

We also sought responses from each agency that, according to our analysis, destroyed kits in cases that could still be prosecuted. We sent each a list of the cases and an opportunity to review and correct any incorrect data and respond to our findings.

We took several steps to verify our underlying data’s accuracy, including checking the data for logical errors, such as kits that were reportedly destroyed before they were collected, or other outliers. We also double-checked dozens of entries by hand, comparing the data against agencies’ original records.

When errors were the result of data entry, we corrected them. When the errors came from records that agencies provided, we contacted those agencies to correct them.

Read how agencies responded to CNN’s reporting here »

Children’s cases

To estimate the number of children’s and teenagers’ rape kits destroyed before the statutes of limitations expired, we sought legal guidance from Marci Hamilton, a law professor and expert in laws around child sex abuse. She is the founder and CEO of CHILD USA, a research and legal advocacy group that focuses on child sex crimes policy.

Calculating the statutes of limitations in cases involving minors must account for the fact that, in some cases, the time limit does not start ticking until the victim reaches legal adulthood.

Hamilton and her team at CHILD USA reviewed records provided by CNN. Together, we identified 47 kits destroyed when there was no statute of limitations or when the statute of limitations had not yet begun or expired.

When some factors, such as the offense date or victim’s age, were unclear, we used the value that resulted in a shorter statute of limitations to ensure that our estimate of improperly destroyed kits was as conservative as possible.

Read more about CHILD USA here »

Springfield

The Springfield Police Department responded to our initial records request by reporting that it destroyed 195 rape kits between 2010 and May 31, 2016. We sought more detail on the agency’s cases because of the large number of kits it reported destroying quickly — at least 90 in less than two years.

We requested reports for those cases and shared 38 with experts. Both reporters and experts noted a variety of persistent shortcomings in the department’s investigations. As a result, we requested and examined the police reports for every case that ended in kit destruction. Altogether, we examined 190 cases. (We did not review reports for three cases in which kits were transferred to other agencies and two cases in which the department could not provide documentation because the cases were dismissed in court.)

To understand Springfield’s investigative shortcomings, we tracked when each case was assigned, to whom, whether the detective pursued any witnesses or suspects, when they closed a case and other details. We then analyzed the data to identify which detectives handled the most cases that ended with destroyed kits, which ones sent 10-day letters to victims (and when) and how often detectives attempted to interview witnesses or suspects.

Our examination of Springfield’s records also turned up 15 cases dating back to 2002 and in which kits were destroyed after suspects pleaded guilty. We consulted two legal experts who reviewed the cases and confirmed that the disposal violated a state law that requires agencies to preserve evidence leading to a conviction.

For our statistics about the number of reported rapes in Springfield, we used data from the Missouri State Highway Patrol.

For the statistics about the number of reported rapes in Springfield, we used data provided by Springfield Chief Paul Williams. The chief was not able to provide data for 2012 because, Williams said, the agency was “missing several months of information for 2012.”

Read Springfield’s response to CNN’s reporting here »

Exonerations

To estimate the number of exonerations linked to the testing of preserved rape kits, we analyzed data from The National Registry of Exonerations, a joint project from the University of California Irvine, University of Michigan and Michigan State University.

The registry provided data, including text summaries, for 466 exonerations in which they identified DNA as a contributing factor.

We then used a word stem analysis — searching for terms that included “test” and “rape” or “sex,” and “swab,” “semen” or “fluid” — to isolate 286 cases potentially involving the testing of a rape kit.

We then read the registry’s summaries for those 286 cases and identified 195 in which the testing of a rape kit or contents of a rape kit (such as swabs, nail clippings or hair) played a role in overturning defendants’ convictions. To vet the registry’s summaries, we examined public records for a sample of the cases.

Read more about the Registry’s data here »