Introduction

The Forensic Science Service (FSS^®) has led the world in the development of DNA databases and DNA automation. The FSS has spent more than six years and several million pounds in research and development to improve and automate the DNA profiling process.

The FSS^® has also spent significant time and money in developing expert systems to support the DNA automation line and to remove the last bottleneck in the automation process - the interpretation of DNA profiles.

The FSS^® processes almost 500,000 DNA samples per annum. There is a significant cost associated with the interpretation of this volume of DNA casework. Using a succession of DNA expert systems the FSS^® has processed more than a million samples in entirely automated DNA lines, with the minimum of involvement from human analysts.

Our research and development has culminated in the production of the FSS-i³ suite of DNA expert systems which we are making available to the forensic community in the USA, Canada, Europe, Australia, New Zealand and other markets.

The FSS-i³ DNA expert system suite

The FSS^® has developed a suite of applications which run under the framework we are calling FSS-i³. In its current format the FSS-i³ suite contains the functionality to analyse and interpret single source DNA profiles, resolve two person DNA mixtures and check batches of data for potential contamination. The individual elements of the suite are:

i-STRess - the core DNA interpretation tool.

i-STRess can analyse and interpret raw DNA data generated with a variety of commercial STR systems - SGMplus^TM, Identifiler, CoFiler, ProFiler Plus and Powerplex 16.

i-STRess designates alleles by the application of a set of heuristics; filters and rules which mimic the process undertaken by a human analyst. The DNA profiles generated can be exported in a user-defined format for input to a laboratory information management system (LIMS), DNA database or for court purposes. i-STRess can also indicate when the profile is likely to contain DNA form more than one contributor and export the results to i-STReam for interpretation.

i-STRess also contains the functionality to undertake a within-batch contamination check. The i-ntegrity module compares the major profiles in each well or lane with those in every other position, highlighting gross contamination or mis-loading events.
i-ntegrity also compares the minor profile in each position with each of the other major profiles, highlighting potential ‘splash over’ contamination events. Finally the application compares the minor components in each position with the minor components in every other position. This is a useful audit tool for detecting very low level contamination in reagents, on plastic ware and in the laboratory environment. No other DNA expert system on the market incorporates this level of anti-contamination checking.

i-STReam – resolving two person DNA mixtures

i-STReam provides a best-fit analysis of two-person mixed DNA profiles using peak height and peak area data and the allele designations determined by i-STRess.

The i-STReam module automates the analysis of mixed DNA profiles enabling previously unusable DNA profiles to be loaded to DNA databases. It can also be used as a stand-alone module to assist the court reporting officer in resolving DNA mixtures, thereby allowing the reporting officer to spend more time on forensic strategy and case interpretation.

Audit functions

All of the FSS-i³ applications generate audit files which indicate exactly how the system performed throughout the analytical process. All of the audit files are date and time stamped and contains the name of the operator and identity of the computer used. If an analyst makes a change to any of the system files or outputs, the software records the changes in the audit logs. The system also has an ‘administrator’ function so that only defined individuals can change settings permanently.

Validation

The FSS-i³ suite of applications has been developed from other, internal FSS^® expert systems. These systems have been extensively validated and tested over the last six years. More than one million DNA profiles have been analysed and loaded to the UK National DNA database using these systems

The FSS-i³ suite has undergone an extensive validation using both DNA database and casework sample data. We are currently preparing a paper for publication which describes this work.

Hardware requirements

The FSS-i³ suite is designed to run on stand-alone PC’s (or from the hard drives of networked PC’s). The system is not designed to run from a server onto ‘thin client’ computers

The system requirements are:

• Windows operating system – Windows 2000 or Windows XP
• 733 MHz Pentium 3 processor or higher
• Microsoft Office 97 (or higher) should be installed

Licensing

The FSS-i³ suite will be provided on an end-user licence basis. The purchase of one software licence will allow the installation of the FSS-i³ suite to a single computer. The license does not limit the number of users of the software.

Installation and training

The FSS^® also offer an installation and optimisation service which is tailored to meet the needs of individual clients.

Support and maintenance

The FSS can supply a service contract for support and maintenance to cover minor upgrades, telephone and e-mail support and technical corrections.

This service does not cover new versions or modules with significant improvements in functionality.

Features and benefits

In our view the business benefits of introducing the FSS-i³ DNA expert system suite include:

• Improved consistency of allele designation by employing a set of objective filters and rules

• A within-batch anti-contamination check in the functionality of the i-ntegrity module

• A reduction in the time required to interpret a batch of DNA data

• A reduction in the unit cost of DNA analysis

• An increased load rate of DNA profiles to DNA databases

• Assists analysts and reporting officers in the resolution of two person mixtures – releasing staff to undertake more valued examinations

• Provides a full audit trail of all functionality

• Completely open architecture – all functionality open to users

• The FSS® developers who designed the FSS-i³ suite are, first and foremost, DNA scientists who understand the problems forensic scientists face

• The mixtures analysis module i-STReam is based on scientific theory developed by leading practitioners such as Dr Peter Gill and Dr Tim Clayton and contained within peer reviewed publications

Contact

We have a specific e-mail account for FSS-i³ enquiries; i_cubed@fss.pnn.police.uk