Archive for the ‘Expert Witness’ Category
Audio Forensic Expert Report Writing
All forensic experts write reports. Some reports are better than others. What goes into a ‘better than other’ forensic report? Depending on the forensic investigation, opening the forensic report with the credibility building language is an important starting point. Here is a sample of how I open my audio forensic reports:
I am an audio forensic expert and have been practicing for 29+ years. I have testified in several courts throughout the United States and worked on various international cases. My forensic practices includeaudio authentication, restoration and voice identification.
The next step in the forensic report is to include the evidence you were provided by your client to forensically examine, as well as what you were asked to do. This paragraph must be documented and described in detail. Here is a sample of how I draft this section:
On or about March, 25, 2011 I received a CD from your office that contains a 911 call recording. You asked that I investigate the recording to determine if it contains one or two voices at the scene of the crime.
I listened to the CD and heard the initial voice that spoke and the second questionable voice in the background, noting that it sounded different from the first voice. I suggested making arrangements to create an exact exemplar of the suspect for comparison purposes in this forensic investigation.
On Tuesday, April 23, you and I arranged to create an exemplar of the suspect’s voice to comparewith the initial 911 call first voice. The exemplar was created using as much of the same electronics as possible that were used in the original 911 call recording. Also featured in the exemplar were the exact cell phone and the same person that placed the original 911 call.
In addition, we also recorded exemplars of other persons who could have made this 911 call for comparisonpurposes in a voice identification line up.
This above outline is an example. Much of the language might not make sense but the text still exemplifies the message I am communicating about audio forensic reports.
The next part includes your investigation; what you did as an audio forensic expert and the opinions you arrived at. This investigative process must list all activity, testing and the software programs, hardware and other tools, scientifically describing in detail all tests so that another forensic expert with similar qualifications can recreate your testing and arrive at conclusions.
In a case where the opposite side in the litigation has retained a forensic expert, that forensic expert will want to review your investigation and findings to determine how to strategize the court proceeding based on this information as well as your opinion. I have worked on cases where the forensics experts were disagreeing with each other before the trial, and others where forensic experts were disqualified before trial. This is why forensic report writing is crucial and one of the most critical parts of any forensic investigation.
The fourth component in the forensic report is the expert’s conclusions; often times this conclusion is ‘based on a reasonable degree of scientific certainty’. The audio forensic expert reports the truth about the evidence in question or another characteristic in question about the audio evidence. The conclusion is a statement of scientific fact and opinions expressed about the conclusion of scientific fact must be presented in simple English for all triers of fact and other expert witnesses to easily understand.
When the forensic report is submitted, it should also include any work product, sub files and the most recent CV (curriculum Vita). If the case is older, chances are the expert has updated their CV since beginning the forensic investigation.
If you have an audio forensic concern and would like more information about the investigating process with regard to report writing, call or write for a pro bono consultation.
The Art and Science of Removing and Restoring Audio From Video
As an audio forensic expert I often receive video evidence that has an audio track that is difficult to understand. Even though the video presents clues and truth about the events as they occurred in the video the audio track also provides an opportunity of clues and events as they occurred to help process the litigation. As both an audio and video forensic expert I am often asked to clarify or enhance the audio from a video. The process of removing the audio track for enhancement and clarification is crucial to the success of presenting the enhanced or clarified audio evidence in court.
First of all, most people look for audio enhancement when they come to me as an audio forensic expert, and I often start our conversation out by explaining to them it’s better to use the word ‘clarify’, because judges and courts don’t understand the semantics and the difference between the words ‘enhanced’ and ‘clarified’. Clarified has less harmful meaning than enhanced. If I’m in court and I tell a judge that I’ve enhanced this audio one of the first things the judge thinks is that something has been done to it to take it or change it from its original state, and that’s not the case. But, most people are educated and search for audio enhancement when they’re looking for an expert to help solve their problem or clarify their evidence.
Removing the audio track to be processed requires the video forensic process of loading the evidence into a software program like Premiere Pro or Final Cut Pro then exporting the audio track in full quality from that video to create a sub-file, which is an audio only file. That file is then imported into Adobe Audition or Sound Forge depending on the nature of the clarification that is necessary. I find Adobe Audition to have more powerful tools to help the clarification process. I use tools in Audition in order to remove unwanted noise and increase the wanted sounds which could be speech, gun noises and other extraneous noises to the environment which could be crucial to the understanding of the events as they occurred. The tools that I use, that I apply to the audio export file, are used in accordance with accepted standards in the scientific community so that if this case were to go court I could explain, by my work product and my notes, what filters or tools were applied to this digital audio file in order to clarify the sounds to be better heard, or the speech to be better understood. Once I’m satisfied with the clarification process and I believe the file has been enhanced as much as possible the exact file, in it’s restored process – which is more clarified and enhanced – is re-imported to the video software program and reconnected to the original video evidence. At that point it is synched with the audio file that was originally part of that video evidence and exported to create the clarified version of that evidence. If there’s any video work that needs to be a part of that process, such as sharpening of the image, zooming in of the video image, that is also done before exporting the new clarified evidence to be used in the litigation. The processes are accepted in the scientific community and an important part of the forensic expert’s job. Keeping track of the steps along the way – including chain of custody of the evidence – is crucial and part of the audio forensic clarification/restoration process.
Audio from Video Evidence Offers Additional Clues
Audio and video forensics go hand in hand in a lot of today’s litigations. As an audio and video forensic expert, I work for both the prosecution as well as the defense. Lately I’ve been working more for the prosecution and I am seeing audio and video evidence being used more often to prosecute cases than ever before. Traditionally defendants would contact me because they believed the police had altered audio and video evidence that was being used in the prosecution’s case. As an expert of almost 29 years, I think about that when I’m contacted by these defendants and wonder why a police officer would risk his reputation, his retirement and his entire career by altering evidence in order to convict. But it’s still my job to authenticate and to investigate when I am asked.
Recently I worked on a case for a police department where there were questions about who said what on a dashcam video. This is where the audio and video forensics intersect in litigation. The dashcam was static and nothing could be seen regarding the series of events as they occurred. However, the microphone in the car and an officer’s microphone were on, allowing the video to record the audio of the situation. What was in question was who said what in the recording. I was able to get samples – or exemplars – of the voices of the people that were at the scene of the crime and compare them to the voices that were recorded on the dashcam video. I had my assistant create a transcription and we started with “voice one, voice two, voice three” because the voices were significantly different (which isn’t always the case). They were different enough that the listener could determine three separate distinct voices. These differences were also an advantage because the voices were all male, which sometimes makes it difficult to differentiate between the parties being recorded. By creating a transcript and determining through voice identification investigation, I was able to recreate what the camera did not see through an audio forensic process.
So when prosecuting a case, it’s important to consider both audio and video aspects of the investigation even if the video may seem hopeless. When you work with an audio and video expert, that expert can give you some advice and ideas of clues that could be picked up in the evidence to help your case. Even if the clues start out small, they may turn into evidence that can be used to help prosecute. The clues will at least bring some more truth into the courtroom, which is the job of the audio and video forensic expert.
The Why and How of Audio Evidence Integrity
When audio recordings are used in any litigation, the integrity of the evidence is not only important, but oftentimes questioned. It’s crucial to consider evidence integrity before you present your evidence in court.
As an audio forensic expert, I am often asked to authenticate audio evidence for litigations. This authentication process provides integrity for the audio evidence and strengthens its weight in the litigation.
For example, it is easy for just about anyone who has some basic computer skills to alter audio evidence by removing portions of the recording that they don’t want the litigators to hear. Although this is not a common practice, it has a huge impact on the credibility of the audio evidence being presented. The reason is as simple as this: the altered audio recording is not an actual representation of the facts as they occurred. Portions of the actual evidence have been removed.
This is similar to missing evidence from a crime scene. What if a police officer arrived at a crime scene and began moving or removing items from the scene? How would the crime scene investigation team know the actual facts of the crime as it occurred without all the evidentiary items at the scene?
Once the integrity of the evidence has been compromised, the audio component of the litigation is reduced to “he said, she said” – my word against theirs.
Police officers have been trained to maintain evidence integrity at the scene of the crime. However, people who submit media evidence like audio and video recordings may not completely understand how important it is to maintain evidence integrity.
Tips to maintain integrity:
1: Keep originals in a safe place.
2: Photograph or video record any specific activity information.
3: Retain a forensic expert to help you document the authenticity of your evidence.
Did George Zimmerman Cry for Help? – The Trayvon Martin Murder Trial
As you probably have read in previous blog postings, I’ve made some comments about the 911 and other police recordings that were involved in the Trayvon Martin shooting case. My opinions were published in the Orlando Sentinel and I also made some appearances on MSNBC and CNN as well as Fox News.
I was contacted by a producer at The Today Show shortly after they acquired a copy of an exemplar that the police made of George Zimmerman’s voice. They made the exemplar (sample of Mr. Zimmerman’s voice) so that it could be compared to the cry for help in the 911 police recording.
The Today Show wanted me to form an opinion and comment while on camera regarding the exemplar that was made by the police. I decided not to go on camera with a comment because the prosecution in this case named me as an expert witness. I did not feel a media update would be appropriate even though the prosecution has yet to contact me since naming me as an expert witness.
However, I do want to go on record and comment that a more appropriate or exact exemplar needs to be made of George Zimmerman’s voice in order to conduct a proper voice identification test.
I believe the police did the best that they could in order to recreate that sample or exemplar of George Zimmerman’s voice. They had him say the word “help” for comparison to the cry for help on the 911 recording. The word “help” was shouted the night this incident took place. The question is who shouted help?
However, what was not done properly when creating the exemplar was the delivery of the word “help” by Zimmerman. The reason being that, it was very different than the long, drawn out scream of help that is heard in the background of the 911 recording which is posted on several places on the Internet. I first learned about that recording from the Mother Jones Blog and, of course, I have discussed it on previous blog posts as well.
I originally formed an opinion that the cry for help was not George Zimmerman’s voice, which was the opinion I shared when asked by the major media. I formed my opinion by using my own critical listening skills that I’ve acquired after 28 plus years as an audio forensic expert who also performs voice identification. No scientific voice identification testing was done because I did not have the proper resources.
The bottom line here is that this has turned into a media frenzy. People in the United States have already formed an opinion as to whether or not Zimmerman is guilty. In some social circles, this case has even taken on a discriminatory slant due to the fact that people are choosing sides based on their own personal views pertaining to racial discrimination.
It’s very unfortunate that Trayvon Martin was shot and killed by George Zimmerman; this is a fact that we know for sure. But it is up to the court and the due process of the United States to determine whether or not George Zimmerman acted in self defense with regard to the shooting.
The way to properly record a voice identification exemplar or sample of the accused voice is to have the person recreate the distance of the cell phone call exactly like the police did. Additionally, the delivery of the words need to be as similar to the original as possible. In this case, I believe that the police could have turned to the FBI for help recording this exemplar.
As an audio forensic expert who has been named as an expert witness in this case, I would have been happy to help create this exemplar as well. And why it was released to the media before consulting with the expert witness team is unknown to me. Below is a link to the audio file that was recorded by the police of George Zimmerman’s voice which was considered an exemplar. Also, s the original 911 call is now. Listen to both of them and decided whether or not it is the voice of George Zimmerman.
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Maintaining Audio Evidence Integrity
Throughout the course of my professional career, the necessity to maintain the integrity and the chain of custody of the original evidence has never changed. As a forensic expert, I am often asked to authenticate and clarify audio and video evidence that is not original, and that does not have a chain of custody that has been maintained. When working for defendants, I make it a point to bring this out in my reports and in my testimony. I often find challenging audio and video evidence containing anomalies or inconsistencies when conducting my forensic examination.
When I work for government agencies and police departments, I guide them through the process of maintaining integrity and a proper chain of custody on audio and video evidence. In fact, I have recently had several cases that involved audio clarification for different police departments.
Frequently, clarification of in-car video or audio tracks simply requires separating the radio chatter from the officer’s microphone. There are a couple of ways that I can do that as a forensic expert. First, in many cases, the radio chatter is on a separate audio track. I load the in-car video in its entirety into my forensic computer and then remove the audio tracks and work on them in Sound Forge to remove the radio chatter. This helps the prosecutor learn more about the audio portion of what went down and why that is important to the case. Other times, I apply compression and equalization to help remove unwanted noise and bring out the speech. Lastly, I lay that audio track back onto the video and export a new digital video file in an mpeg format so that it can be burned to a DVD. This process does not change the integrity of the evidence and my forensic documentation contains of all of the steps that I took so that I can maintain the chain of custody on the evidence as well as its integrity. This processes that I use is acceptable in the scientific community as well.
In litigation, sometimes the small facts about a video or audio recording are important. When those facts are difficult to see or hear, police departments and other litigators look to an audio forensic expert to help them better understand portions of a recording that are not as clear as was hoped when the recording was made. It could be because of wind noise, background cars passing by on the highway, or distortion from a microphone transmitter.
There are a number of things that can distort an audio recording, but a forensic expert can use multiple techniques to help restore the audio so we can better understand the facts as they occurred. A forensic expert’s role in litigation is very important. As an expert, he or she can help courts interpret the process of exporting the original evidence from the digital recorders, the chain of custody and the purpose of the processes that were applied to the evidence to help restore both sound and vision. Finally, a forensic expert presents these processes and the evidence in court–keeping it easy for the court to understand the facts as they occurred.
The Trayvon Martin Killing – In the Media and the Press
Over the last few days, I’ve been contacted by news sources wanting to interview me about voice identification. Some 911 recordings had been released a week prior from the Trayvon Martin case out of Florida.
Reporters asked me about voice identification reliability. Voice identification is a reliable science when done properly. Trying to determine who is screaming in the background of a 911 call is not easy but seems to be of great significance since these were the final hours of this young man’s life.
I became interested in this case and decided to listen to and peruse the 911 recordings.
I literally stumbled upon the link of 911 calls from http://motherjones.com/politics/2012/03/what-happened-trayvon-martin-explained#transcript
I listened to the 911 calls and recorded them into my audio forensic computer to critically listen to the events. Two of the 911 calls are very interesting: George Zimmerman’s call and the woman who called 911 when she heard screaming outside her home (which we can hear clearly in her 911 call recording).
This second recording is the same recording where the gun shot is heard that killed Trayvon.
I am not writing this to judge but rather to present the facts as they occurred from a forensic perspective.
As an audio forensic expert I want to make clear that this is not formal voice identification and not meant for legal purposes. It is not a statement of my opinion but rather a presentation of facts as I hear them in two particular 911 recordings. I believe you will hear what I hear.
Listen carefully to the 911 call segment I chose from George Zimmerman. Then listen to the tone of the male voice screaming for help in the background during the second 911 call. Can you see the series of events in your mind’s eye?
Are Audio Forensic Procedures Reliable in the Legal System?
How reliable are audio forensic procedures in the legal system? A student recently asked me that and asked about some of the ins and outs of a career in audio forensics. The student’s specific questions are below and are followed by my answers.
1. How often is speech-based evidence used in court? It’s used very often. Voice identification evidence helps a court to identify people involved in a case and put the puzzle pieces of a case together. Furthermore, voice identification can also sometimes provide substantial enough evidence to cause people to be convicted or released.
Is it a common or rare occurrence? Our business has grown significantly, so I would say that audio forensic procedures in the legal system are common.
2. Is voice identification a lengthy process? It can take up to 4 hours for the average case. This includes 3 types of examination. Audio forensic experts visually examine the sound wave, comparing the evidence and an exemplar (a voice sample of the accused). Next, Audio forensic experts electronically measure the evidence, which is then compared to the exemplar. Finally, and most importantly, audio forensic experts critically listen to compare how the words are spoken and pronounced in the evidence and the exemplar.
3. Are there any factors which can create problems when dealing with a recording? Yes, difference in age between the recording in question and the creation of the exemplar creates problems. People’s voices change with the passing of time. One of the nationally accepted standards for comparing voices is that the voice samples must not be more than six (6) years apart.
4. Is voice identification considered to be reliable within the legal system? YES. However, it’s argued more in some states than others. The forensic expert must carefully examine all scientific evidence and follow procedures. Both law enforcement and defendants seek assistance from audio forensic experts.
Can’t Convict on Less Than 20 Words
Since I began my career as an audio forensic expert 28 years ago, I have been retained on two drug trafficking cases where the US prosecutors office was trying to convict based on five words spoken during a confidential informant recording.
I have been on both sides of the fence working for the state as well as for the defense. The scientific community, specifically the American Board of Recorded Evidence, explicitly states that in order for an audio forensic expert to deliver a positive identification, “At least 90% of all comparable words must be very similar aurally and spectrally, producing not less than twenty (20) matching words. The voice samples must not be more than six (6) years apart.”
Voice identification is both an art and a science. It is an art in that the forensic examiner has to conform best practices to each specific, unique case. Not all voice identification cases are the same. In fact, I have had related situations but every case has still been unique.
I have identified singers, good guys and bad guys. I have testified in cases where my testimony was crucial in the outcome of the case. One thing remains certain: a government body cannot convict because they believe a specific person said the phrase that their case is built around.
For example, imagine I am with three other friends and after a confidential informant approaches me inquiring about a crime we are plotting, one of us in the group says the “phrase that pays” in order for the CI to complete the sting. Unless that CI’s recording has a 20 or more word “phrase that pays” it’s technically their word against the defendants about who said the convicting phrase.
In other words, the difference between first degree murder and the death penalty vs. a lesser judgment could be that phrase spoken during the recording and the person who spoke that phrase on the CI recording.
An audio forensic expert has the ability to identify that voice by creating an exemplar and comparing at least 20 words, no fewer, spoken by the accused. I recently had a case where the state was going for a more severe conviction based on five words spoken during a CI recording. However, it is not possible to deliver a positive identification based on so few words.
Is It Still Elvis Presley? Cast Your Vote
Last Monday I did another radio interview for Elvis Express Radio. Joe from the network called me about 10 am EST and asked how I knew this song had Elvis Presley singing. I explained to him that I did forensic voice identification and compared the vocal to similar types of Elvis songs from around the same time. ‘What Now My Love’ was one of the songs I used as an exemplar, which is the second step when I conduct voice identification. In this case an exact exemplar could not be created for obvious reasons so we went with songs that were recorded around the same time and had similar vocal innovation.
We would like to know what you think about the new song. Do you believe its Elvis Presley?
Joe from Elvis Express radio told me during my interview that he had been an Elvis fan for 40 years and he believed that “Living to Love You” was not sung by Elvis Presley. I told him that I respected his opinion and we concluded the interview.
I did not think much of it because I have been an audio engineer working with world renowned and local musicians and artists as well as a forensic expert for 27+ years. Of course I could be wrong; there is always a margin of error in any voice identification.
Today I received an email from the lawyer handling the sale of the song. Her update is very interesting. She hired author Tom Grace who is an Elvis expert to listen to the song and review the documents.
Tom has positive feedback regarding my forensic analysis. After he listened to the tape he confirmed that it had to be Elvis for a different reason than my forensic voice analysis determined.
“No one would try to make a tape to sound like Elvis with such a poor arrangement” was his first comment. The instruments were all out of balance including the piano. Tom said he could hear the piano and he believes he knows who the piano player was and who was playing the guitar and base.
He has researched the date and time that everyone was together and came up with February 24, 1965 in Nashville when they were recording the soundtrack for the Elvis movie “Harum Scarum.” There are three recordings documented from 11:00 p.m. to Feb 25 at 1:00 a.m.
He does not know what was recorded other than they worked on one record which was for “Harum Scarum.” The recording was not put on a reel and must have been direct to acetate because there is a popping sound in it. It was not copy written until 1976; a letter to Albert Lee states copy writing does not normally occur until the song is published.
Speculation is that Jimmie Crain heard that Elvis wasn’t doing well in 1976, so he checked and found the song had not been previously copy written by RCA . He apparently decided to copy write it before something happened to Elvis.
Tom Grace will be publishing his findings and the lawyer representing the sale of the song, Violet Hinton, has contacted WWMT TV 3 to interview Tom Grace in a follow up story.
If you believe this song is Elvis Presley, hit the like button on the article link on Audio Forensic Expert’s Facebook page. You can also email us at Primeau@PrimeauProductions.com.
